Will repost in the morning
My Pond Filter Project
- Thread starter ed2
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Nice description of all you did, the good the bad the ugly!, but for some reason your photos don't show,
Pond Filter Design
The Pond
My pond was first established some many years ago when I was around 10 years of age. The pond was originally intended to hold a few goldfish, after I had pestered my parents for many years that I wanted some fish. Finally, my dad gave in, dug me a hole, lined it and filled it with water, popped some fish, water lillies and reeds in, and that was as sophisticated as the pond was. It was 2 feet deep, with a walled edge surrounding it, and a bridge across the centre to access a nice wooden decking area.
10 years later, the pond had fallen into a state of disrepair. Over the 8 years, predator attacks and 10 winters had got the best of the fish, and there were none left in the pond. As a wildlife pond, however, the pond couldn’t have been better! There were literally hundreds of newts, many frogs and millions of weird and wonderful insects. The pond wasn’t enjoyed as it was. It looked a mess and was a bit of a disgrace, since the rest of the garden had been renovated nicely, so we faced a decision – fill it in or give it an overhaul. I took this opportunity to finally take control and to establish a mixed pond to keep some newts and a variety of fish happy, but to be able to house some pretty koi too.
So, to cut a long story short, I overhauled the pond by completely draining it, relining it and making it 3 feet deep, with a raised flower bed to discourage unwanted predators (particularly herons!)
The pond is now approximately 10,000 litres in volume and is a home to a group of very happy fish – namely six 12 inch ghost carp, one 8 inch ghost carp, one 8 inch mirror carp, three 6 inch goldfish and two 4 inch goldfish. The pond is also the home to well over 100 newts, that have all found their way into the pond over time.
Please Note: This picture shows only half of the pond
The Issue
I fell into the trap. I managed to be persuaded, probably encouraged by the copious amounts of brands and models, and reviews stating how wonderful the products are, into buying a pressurised filter for my pond. I cannot deny that it worked reasonably well, at least for as long as I didn’t mind cleaning it out every day. The chemical levels were pretty good in the pond, but the filter sponges just became saturated with debris and waste on an almost daily basis, necessitating a lot of time and effort to be invested in maintenance. The issue with this is that I’m at university and live away from my family home through the week and my parents can’t commit the time to clean the filters. I can’t say I blame them, it’s an absolute nightmare!
Whilst the chemical levels were ideal for the fish, the main idea of keeping fish in a pond is to be able to see them! Regretfully, the pressurised filters just were not adequate to filter the debris efficiently, and as such the water clarity just wasn’t good enough to enjoy the pond properly. The clarity issue can be seen in the following pictures:
The Solution?
The pond keeping is a real hobby of mine, and the more I read online, the more I learn, and so my pond management is constantly changing. It was whilst browsing and reading around different pond designs that I came across a really good filter design on a gentleman’s website (http://kilk.com/pond). This filter seemed like a really good design, and certainly seems to work for Erik on a much larger pond than my own. I adopt his ideas and to incorporate a planted gravel filter into my pond filtration system.
I took the basic design of the gravel filter and played around with some ideas to come up with something that I thought could be a better design for the filter. Erik had identified that his water was cycling through his filter bed too quickly, which meant that whilst it an effective filter, it could benefit from filtering the water more slowly. The design I had found had an inlet pipe with many holes drilled lay beneath a bed of gravel. The water was pumped up and through the gravel, before being gravity fed back into the pond. Because I wanted my water to take longer to flow through the gravel, I decided to use an inlet pipe at one end of the filter, thus forcing the water to travel horizontally through the gravel bed, rather than rising through just a foot of gravel.
This is the design I came up with originally:
I thought originally that it would be a good idea to use the pressurised filters as a pre-filter, but after seeking advice on several forums, it was decided that this wasn’t going to be of any benefit. It would still require frequent cleaning and would only do what the gravel filter was designed to do anyway, but on a much smaller and less effective scale. Instead, I considered the use of filter brushes to catch larger debris. Again, however, I decided to avoid buying these expensive brushes initially to see how it worked without them, since the gravel wouldn’t allow debris to pass through it. I have also removed the section with barley straw, as I decided this shouldn’t be necessary with the water cress in the filter too.
My filter design also uses a 6 inch sump. This sump is designed to allow for the debris and waste to fall into the base of the filter, and to run downwards towards the drain. On cleaning, the drain can be opened, and all of the waste will be flushed from the sump of the filter. The theory of this design was that it would allow for more regular mini cleans, which would negate the need to drain the water completely and remove all of the gravel to clean it, before putting everything back together again. Erik had retrofitted a draining function to his filter to allow for the same function. The drain was fitted at end of the filter, rather than in the middle, for access reasons.
The filter is a retro-fit to a pond that was built around 12 years ago now. With the filter being an afterthought, I needed to find a location and use the space I could gain. The requirements for the filter were that it needed to be quite large, receive a good amount of sunlight for the vegetation and above all it had to be above the height of the pond. It just so happened that I found the ideal place to locate the filter, behind the pond. Luckily, the area I identified was directly behind the current waterfall that was already in situ in the corner of the pond:
In order to build the filter, I needed to gain access to the space that was behind the decking. The first step was to cut through this clematis and take it away completely:
Once this was stripped back, following some 60 minutes of frustrating weeding, carefully cutting around the wooden trellis, I had to find a way to access the space behind:
It was decided that the easiest way to do this was to cut a large square section of the wooden trellis and to remove this, and to fit hinges to form a gate for access to the space behind the decking.
Continued Below:
The Pond
My pond was first established some many years ago when I was around 10 years of age. The pond was originally intended to hold a few goldfish, after I had pestered my parents for many years that I wanted some fish. Finally, my dad gave in, dug me a hole, lined it and filled it with water, popped some fish, water lillies and reeds in, and that was as sophisticated as the pond was. It was 2 feet deep, with a walled edge surrounding it, and a bridge across the centre to access a nice wooden decking area.
10 years later, the pond had fallen into a state of disrepair. Over the 8 years, predator attacks and 10 winters had got the best of the fish, and there were none left in the pond. As a wildlife pond, however, the pond couldn’t have been better! There were literally hundreds of newts, many frogs and millions of weird and wonderful insects. The pond wasn’t enjoyed as it was. It looked a mess and was a bit of a disgrace, since the rest of the garden had been renovated nicely, so we faced a decision – fill it in or give it an overhaul. I took this opportunity to finally take control and to establish a mixed pond to keep some newts and a variety of fish happy, but to be able to house some pretty koi too.
So, to cut a long story short, I overhauled the pond by completely draining it, relining it and making it 3 feet deep, with a raised flower bed to discourage unwanted predators (particularly herons!)
The pond is now approximately 10,000 litres in volume and is a home to a group of very happy fish – namely six 12 inch ghost carp, one 8 inch ghost carp, one 8 inch mirror carp, three 6 inch goldfish and two 4 inch goldfish. The pond is also the home to well over 100 newts, that have all found their way into the pond over time.
Please Note: This picture shows only half of the pond
The Issue
I fell into the trap. I managed to be persuaded, probably encouraged by the copious amounts of brands and models, and reviews stating how wonderful the products are, into buying a pressurised filter for my pond. I cannot deny that it worked reasonably well, at least for as long as I didn’t mind cleaning it out every day. The chemical levels were pretty good in the pond, but the filter sponges just became saturated with debris and waste on an almost daily basis, necessitating a lot of time and effort to be invested in maintenance. The issue with this is that I’m at university and live away from my family home through the week and my parents can’t commit the time to clean the filters. I can’t say I blame them, it’s an absolute nightmare!
Whilst the chemical levels were ideal for the fish, the main idea of keeping fish in a pond is to be able to see them! Regretfully, the pressurised filters just were not adequate to filter the debris efficiently, and as such the water clarity just wasn’t good enough to enjoy the pond properly. The clarity issue can be seen in the following pictures:
The Solution?
The pond keeping is a real hobby of mine, and the more I read online, the more I learn, and so my pond management is constantly changing. It was whilst browsing and reading around different pond designs that I came across a really good filter design on a gentleman’s website (http://kilk.com/pond). This filter seemed like a really good design, and certainly seems to work for Erik on a much larger pond than my own. I adopt his ideas and to incorporate a planted gravel filter into my pond filtration system.
I took the basic design of the gravel filter and played around with some ideas to come up with something that I thought could be a better design for the filter. Erik had identified that his water was cycling through his filter bed too quickly, which meant that whilst it an effective filter, it could benefit from filtering the water more slowly. The design I had found had an inlet pipe with many holes drilled lay beneath a bed of gravel. The water was pumped up and through the gravel, before being gravity fed back into the pond. Because I wanted my water to take longer to flow through the gravel, I decided to use an inlet pipe at one end of the filter, thus forcing the water to travel horizontally through the gravel bed, rather than rising through just a foot of gravel.
This is the design I came up with originally:
I thought originally that it would be a good idea to use the pressurised filters as a pre-filter, but after seeking advice on several forums, it was decided that this wasn’t going to be of any benefit. It would still require frequent cleaning and would only do what the gravel filter was designed to do anyway, but on a much smaller and less effective scale. Instead, I considered the use of filter brushes to catch larger debris. Again, however, I decided to avoid buying these expensive brushes initially to see how it worked without them, since the gravel wouldn’t allow debris to pass through it. I have also removed the section with barley straw, as I decided this shouldn’t be necessary with the water cress in the filter too.
My filter design also uses a 6 inch sump. This sump is designed to allow for the debris and waste to fall into the base of the filter, and to run downwards towards the drain. On cleaning, the drain can be opened, and all of the waste will be flushed from the sump of the filter. The theory of this design was that it would allow for more regular mini cleans, which would negate the need to drain the water completely and remove all of the gravel to clean it, before putting everything back together again. Erik had retrofitted a draining function to his filter to allow for the same function. The drain was fitted at end of the filter, rather than in the middle, for access reasons.
The filter is a retro-fit to a pond that was built around 12 years ago now. With the filter being an afterthought, I needed to find a location and use the space I could gain. The requirements for the filter were that it needed to be quite large, receive a good amount of sunlight for the vegetation and above all it had to be above the height of the pond. It just so happened that I found the ideal place to locate the filter, behind the pond. Luckily, the area I identified was directly behind the current waterfall that was already in situ in the corner of the pond:
In order to build the filter, I needed to gain access to the space that was behind the decking. The first step was to cut through this clematis and take it away completely:
Once this was stripped back, following some 60 minutes of frustrating weeding, carefully cutting around the wooden trellis, I had to find a way to access the space behind:
It was decided that the easiest way to do this was to cut a large square section of the wooden trellis and to remove this, and to fit hinges to form a gate for access to the space behind the decking.
Continued Below:
Once behind, it was just a case of clearing back the overgrown weeds to inspect the area and to be sure that it was a suitable location for the filter.
Once the weeds had been cleared, following another 60 minutes work, it was relieving to find that the site was perfect to fit the filter.
Measurements were made and the timber was ordered. For the frame, it was decided that we would use the fence to form one side of the filter, and the frame of the decking to form the opposite side. I placed 6x1 (inches) timber on both sides to form the sides of the filter.
I then used 3x2 (inches) timber to form a frame to fit the 6x1 at either end of the filter, as shown below:
Once the ends were in place, the frame for the filter was completed. The frame was constructed with dimensions 12 feet length and 3 feet depth. At the inlet end, the filter was 1.5 feet wide, whilst at the outlet end; the filter was 3 feet wide, due to the constraints of the decking and fence. This was the maximum size that could be accommodated, and was believed to be adequate for the size of my pond.
The next step was to form a slope on the base of the filter, to allow for the debris and waste to collect at the drain of the filter, thus enabling easy maintenance of the system. This was achieved using some paving slabs that were surplus to requirements from a previous patio build in the garden:
Because the filter was designed to gravity feed back into the pond, it was necessary for the inlet pipe from the pond pump to be at the far end of the filter. To keep things tidy, I decided to run 1.5” diameter PVC pipe underneath the base of the filter, before rising on the far side of the filter and allowing the water to fall from above. I ran the 1.5” pipe inside a larger pipe under the base of the filter, in order to better protect the pipe from frost and from any sharp objects that could penetrate the pipe from the ground. By running the inlet pipe through a larger pipe, it also allows any leaks under the filter to be identified, as the water will run out either side of the filter, rather than just sinking under the filter straight into the ground.
It was my intention to run 1.5” flexi pipe into the PVC pipe, and so it was necessary to find a connector that was suitable. I found that the hosetail attachment from my pressurised filter fit the PVC pipe perfectly, and thus the solution to connect the two different types of pipe.
I then added sand and soft carpet to the base, to help prevent any sharp edges penetrating the bottom of the pond liner from the ground beneath. Soft building sand was then spread along the top to finish the base, ready for the liner:
I also used a spirit level to ensure that there was a slight slope downwards, running to the drain.
I decided that I would use two liners on the filter, in an attempt to maximise the lifespan of the filter. As a pre-liner, I used a cheap tarpaulin that I bought from a local garden centre, just in case any strong plants did start to grow under the base at any time. I also ran 9 foot lengths of 3x3 (inches) timber to help to suspend the gravel above the sump. This timber ran underneath the liners and was designed to encourage the drainage of waste, by creating two channels narrower channels.
A normal butyl liner was then applied over the top of the pre-liner. I took great care with both liners to ensure that their integrity remained intact and that there would be no nasty surprise leaks when I added water to the filter.
To complete the sump, I placed 3x2 (inches) treated timber horizontally, suspended above the long wood, which provided the 6 inch deep sump. I placed galvanised and treated wire mesh (like chicken pen wire) over the 3x2 timber supports. This would provide my base to suspend the gravel above the sump, but the mesh was too large for the gravel, so I also added some plastic mesh of a fine diameter above the wire fencing. The aim was to try to prevent the restriction of water flow, and to allow debris to fall into the sump through the wire.
It was necessary to wash the pea gravel, as there was a lot of soil and dirt from the ground. I decided to do this once the gravel was in the filter, as this allowed me to clean the gravel without flooding my garden and also allowed me to evaluate the integrity of the drain fitting.
I slowly increased the layers of gravel, washing it layer by layer. It took 2 days to fill the filter, which held 1.2 tonnes (1,200 kilograms) of pea gravel.
In order to fill the filter without draining the pond, I decided it was necessary for me to fill the filter from the garden hose pipe. The pH level in my tap water is 8.5, however my pond water is slightly higher at 9.0, so it was lucky for me that I could reduce the pH slightly by adding tap water. I used dechlorinating chemicals when I filled the filter, and I left the water to stand for a couple of days too, to avoid harm to my fish and plants from the tap water chemicals. This also allowed the temperature of the water in the filter to balance with the pond water, to avoid stressing the fish.
Once the filter was reasonably full, I started to fit the tank connectors, which I would use to cross the liner and the wooden frame. These were purchased from the local plumbing centre at a low cost (especially compared to aquatics branded bulkheads/tank connectors, which do the same thing!). In order to allow for a better seal, I decided to flush mount the tank connectors. To do this, I used a large diameter hole saw and drilled it in until it was around 5mm into the wood. I then removed this and selected the correct diameter (smaller) bit for the tank connector to pass through the wood, and drilled through the wooden frame.
In order to fit the tank connector with a tight fit, I cut the liners with scissors to ensure that there were no leaks. I used silicon based sealant to seal the connections.
I then used a chisel to remove the outer diameter that I had cut with the larger hole saw, to allow a snug fit.
I originally placed two tank connectors as outlets, with a third small diameter tank connector higher up in the filter to act as an emergency overflow, should any problems arise. This is a precautionary measure to buy time, if the filter suddenly became saturated and started to overflow. Upon filling the filter, it immediately became apparent that the two outlets were not enough to deal with the high demand from my Hozelock Titan 5500. This did allow me to find that the overflow did its job well, and prevented losing any water and draining the pond! Since, I have added a further two outlets. I have placed one outlet running through the waterfall to return to the pond, whilst all of the other outlets and the overflow run through flexi pipes under the waterfall to return to the pond. This is simply because the waterfall cannot cope with the high volume of water from more than one pipe.
Please note: This picture shows just the two original outlet pipes and the overflow pipe. I have since added two more outlets to the filter, which are adequate for the high flowrate.
To finish off, I built a hinged lid to cover the pipework at the outlet end of the pond. I simply used two short pieces of 6x1 (inches) wood, with hinges on one end. I connected these with offcuts of the half-round fence wood that I hadn’t used, to form a lid. I then placed an old wardrobe opening mechanism to the lid to hold the lid open whilst working on the outlets or inlet of the filter. The box also allows for a great storage area for the fish foods, which is really convenient and keeps the food out of direct sunlight and safe from animals and rodents.
In the early stages of the project, I bought some watercress in a bag from a supermarket. This was cheaper than buying a rooting plant. I simply threw the bag full into the pond and left it for a couple of weeks. The watercress has now rooted and will be put into the filter soon.
In conclusion, the filter has now been running for three days. The water is already crystal clear, and the chemical balances are still within ideal ranges! The filter has cost a fair amount to construct, but when compared to the cost of a new pressurised filter, it costs around the same amount of money, plus a bit of elbow grease, to gain 100 x the filter! I would recommend this design to anybody!
Bad Points and Learning the Hard Way
What I Used and What It Cost:
Timber
Total Cost: £94.00 Including Delivery
Plumbing
Total Cost: £85
Liners
Total Cost: £45
Gravel and Sand
Total Cost: £67
Miscellaneous
Total Cost: £19
Overall Project Cost:
£310
In all, I feel that this project has been really successful. I expected there to be some problems along the way, but luckily these have been relatively minor. Should the problem with the bowing sides get worse, I can empty the filter and strengthen the sides very easily by adding in long beams of 3x3 wood externally to help keep everything square. At the moment, I'm not too concerned. The water is now, just a few days after the completion, virtually crystal clear again! I can only assume that the pressurised filters were just become saturated too quickly and so not able to collect all of the debris from the pond efficiently.
Originally, I had planned that once the water became clear (which I anticipated would take a lot longer!), to drain the filter to clean the debris. Now that I have cleaned the water in the pond adequately, I have looked and the filter hardly looks dirty. The sump has worked exactly as planned and has a very thin layer of dirt in it, but it isn't enough to warrant draining the filter and disturbing the beneficial bacteria.
I am aware this isn't a sophisticated filtration system compared to many, however its simplistic design seems to be doing exactly what I need it to do! I have also left an area around the corner from the filter behind the decking, which is a space of 40 feet long x 3 feet wide. This can be used to add in a pre-filter or venturi, etc, should I wish to do so at a later date. To be honest, I'm fairly sure this will never be necessary, with such a hugely oversized filter. Erik's filter is slightly larger but holds around 5% of his large pond's volume. I believe my filter probably holds around 33% of my pond's volume.
Once the weeds had been cleared, following another 60 minutes work, it was relieving to find that the site was perfect to fit the filter.
Measurements were made and the timber was ordered. For the frame, it was decided that we would use the fence to form one side of the filter, and the frame of the decking to form the opposite side. I placed 6x1 (inches) timber on both sides to form the sides of the filter.
I then used 3x2 (inches) timber to form a frame to fit the 6x1 at either end of the filter, as shown below:
Once the ends were in place, the frame for the filter was completed. The frame was constructed with dimensions 12 feet length and 3 feet depth. At the inlet end, the filter was 1.5 feet wide, whilst at the outlet end; the filter was 3 feet wide, due to the constraints of the decking and fence. This was the maximum size that could be accommodated, and was believed to be adequate for the size of my pond.
The next step was to form a slope on the base of the filter, to allow for the debris and waste to collect at the drain of the filter, thus enabling easy maintenance of the system. This was achieved using some paving slabs that were surplus to requirements from a previous patio build in the garden:
Because the filter was designed to gravity feed back into the pond, it was necessary for the inlet pipe from the pond pump to be at the far end of the filter. To keep things tidy, I decided to run 1.5” diameter PVC pipe underneath the base of the filter, before rising on the far side of the filter and allowing the water to fall from above. I ran the 1.5” pipe inside a larger pipe under the base of the filter, in order to better protect the pipe from frost and from any sharp objects that could penetrate the pipe from the ground. By running the inlet pipe through a larger pipe, it also allows any leaks under the filter to be identified, as the water will run out either side of the filter, rather than just sinking under the filter straight into the ground.
It was my intention to run 1.5” flexi pipe into the PVC pipe, and so it was necessary to find a connector that was suitable. I found that the hosetail attachment from my pressurised filter fit the PVC pipe perfectly, and thus the solution to connect the two different types of pipe.
I then added sand and soft carpet to the base, to help prevent any sharp edges penetrating the bottom of the pond liner from the ground beneath. Soft building sand was then spread along the top to finish the base, ready for the liner:
I also used a spirit level to ensure that there was a slight slope downwards, running to the drain.
I decided that I would use two liners on the filter, in an attempt to maximise the lifespan of the filter. As a pre-liner, I used a cheap tarpaulin that I bought from a local garden centre, just in case any strong plants did start to grow under the base at any time. I also ran 9 foot lengths of 3x3 (inches) timber to help to suspend the gravel above the sump. This timber ran underneath the liners and was designed to encourage the drainage of waste, by creating two channels narrower channels.
A normal butyl liner was then applied over the top of the pre-liner. I took great care with both liners to ensure that their integrity remained intact and that there would be no nasty surprise leaks when I added water to the filter.
To complete the sump, I placed 3x2 (inches) treated timber horizontally, suspended above the long wood, which provided the 6 inch deep sump. I placed galvanised and treated wire mesh (like chicken pen wire) over the 3x2 timber supports. This would provide my base to suspend the gravel above the sump, but the mesh was too large for the gravel, so I also added some plastic mesh of a fine diameter above the wire fencing. The aim was to try to prevent the restriction of water flow, and to allow debris to fall into the sump through the wire.
It was necessary to wash the pea gravel, as there was a lot of soil and dirt from the ground. I decided to do this once the gravel was in the filter, as this allowed me to clean the gravel without flooding my garden and also allowed me to evaluate the integrity of the drain fitting.
I slowly increased the layers of gravel, washing it layer by layer. It took 2 days to fill the filter, which held 1.2 tonnes (1,200 kilograms) of pea gravel.
In order to fill the filter without draining the pond, I decided it was necessary for me to fill the filter from the garden hose pipe. The pH level in my tap water is 8.5, however my pond water is slightly higher at 9.0, so it was lucky for me that I could reduce the pH slightly by adding tap water. I used dechlorinating chemicals when I filled the filter, and I left the water to stand for a couple of days too, to avoid harm to my fish and plants from the tap water chemicals. This also allowed the temperature of the water in the filter to balance with the pond water, to avoid stressing the fish.
Once the filter was reasonably full, I started to fit the tank connectors, which I would use to cross the liner and the wooden frame. These were purchased from the local plumbing centre at a low cost (especially compared to aquatics branded bulkheads/tank connectors, which do the same thing!). In order to allow for a better seal, I decided to flush mount the tank connectors. To do this, I used a large diameter hole saw and drilled it in until it was around 5mm into the wood. I then removed this and selected the correct diameter (smaller) bit for the tank connector to pass through the wood, and drilled through the wooden frame.
In order to fit the tank connector with a tight fit, I cut the liners with scissors to ensure that there were no leaks. I used silicon based sealant to seal the connections.
I then used a chisel to remove the outer diameter that I had cut with the larger hole saw, to allow a snug fit.
I originally placed two tank connectors as outlets, with a third small diameter tank connector higher up in the filter to act as an emergency overflow, should any problems arise. This is a precautionary measure to buy time, if the filter suddenly became saturated and started to overflow. Upon filling the filter, it immediately became apparent that the two outlets were not enough to deal with the high demand from my Hozelock Titan 5500. This did allow me to find that the overflow did its job well, and prevented losing any water and draining the pond! Since, I have added a further two outlets. I have placed one outlet running through the waterfall to return to the pond, whilst all of the other outlets and the overflow run through flexi pipes under the waterfall to return to the pond. This is simply because the waterfall cannot cope with the high volume of water from more than one pipe.
Please note: This picture shows just the two original outlet pipes and the overflow pipe. I have since added two more outlets to the filter, which are adequate for the high flowrate.
To finish off, I built a hinged lid to cover the pipework at the outlet end of the pond. I simply used two short pieces of 6x1 (inches) wood, with hinges on one end. I connected these with offcuts of the half-round fence wood that I hadn’t used, to form a lid. I then placed an old wardrobe opening mechanism to the lid to hold the lid open whilst working on the outlets or inlet of the filter. The box also allows for a great storage area for the fish foods, which is really convenient and keeps the food out of direct sunlight and safe from animals and rodents.
In the early stages of the project, I bought some watercress in a bag from a supermarket. This was cheaper than buying a rooting plant. I simply threw the bag full into the pond and left it for a couple of weeks. The watercress has now rooted and will be put into the filter soon.
In conclusion, the filter has now been running for three days. The water is already crystal clear, and the chemical balances are still within ideal ranges! The filter has cost a fair amount to construct, but when compared to the cost of a new pressurised filter, it costs around the same amount of money, plus a bit of elbow grease, to gain 100 x the filter! I would recommend this design to anybody!
Bad Points and Learning the Hard Way
- Being a student, I always try to go for a bargain! This caught me out when I paid for a second hand liner, which I was assured was of good quality and had no holes. It had supposedly only been removed from the seller’s pond since he had closed it down. This was rubbish, and I would never buy second hand again, since sadly some people cannot be trusted!
- The 6x1 (inches) timber, which I fitted in 4 metre lengths, has bowed significantly under the high pressure inside the filter (from the gravel and water pushing outwards). This has left the whole decking frame bent inwards, and the fence on the other side bowed outwards. I would certainly use stronger timber for the frame if I was building a filter again!
- I would use wider bore outlet pipes. I anticipated this would be an issue, but I thought I would give it a try. The problem was that I had already secured and fitted the waterfall, and wanted to use flexi pond pipe to run underneath this in the soil bank. I would have had to use very large rigid pipework and would have had to dig up the waterfall in order to accommodate this. Now I have four outlets, this isn’t an issue anymore
- I decided to try having the inlet spraying water from above the water level of the filter, to help get some oxygen into the filter. After a few days, it became apparent that too much water was splashing out of the filter, so I added a down pipe to carry the water directly into the filter, which has stopped the splashing altogether, and thus the water level has balanced out
What I Used and What It Cost:
Timber
- Ten lengths of 6x1 (inches) wood in 4 metre lengths
- Five lengths of half-round wood in 4 metre lengths
- Two lengths of 3 x 2 (inches) wood in 4 metre lengths
Total Cost: £94.00 Including Delivery
Plumbing
- Four lengths of 1.5” PVC pipe
- One length of 4” PVC pipe
- Six tank connectors
- Eleven metres of 1.5” flexi hose
- Two tubes silicon sealer
- Various plumbing joints
Total Cost: £85
Liners
- Tarpaulin 6m x 3m
- Pond liner 5.5m x 3m
- Second hand liner (later discarded due to damage)
Total Cost: £45
Gravel and Sand
- Sand £12 for 10 bags
- Gravel £55 (delivered)
Total Cost: £67
Miscellaneous
- Wire mesh: £16
- Plastic mesh: £3
Total Cost: £19
Overall Project Cost:
£310
In all, I feel that this project has been really successful. I expected there to be some problems along the way, but luckily these have been relatively minor. Should the problem with the bowing sides get worse, I can empty the filter and strengthen the sides very easily by adding in long beams of 3x3 wood externally to help keep everything square. At the moment, I'm not too concerned. The water is now, just a few days after the completion, virtually crystal clear again! I can only assume that the pressurised filters were just become saturated too quickly and so not able to collect all of the debris from the pond efficiently.
Originally, I had planned that once the water became clear (which I anticipated would take a lot longer!), to drain the filter to clean the debris. Now that I have cleaned the water in the pond adequately, I have looked and the filter hardly looks dirty. The sump has worked exactly as planned and has a very thin layer of dirt in it, but it isn't enough to warrant draining the filter and disturbing the beneficial bacteria.
I am aware this isn't a sophisticated filtration system compared to many, however its simplistic design seems to be doing exactly what I need it to do! I have also left an area around the corner from the filter behind the decking, which is a space of 40 feet long x 3 feet wide. This can be used to add in a pre-filter or venturi, etc, should I wish to do so at a later date. To be honest, I'm fairly sure this will never be necessary, with such a hugely oversized filter. Erik's filter is slightly larger but holds around 5% of his large pond's volume. I believe my filter probably holds around 33% of my pond's volume.
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Wonderful job and description. Great filter design. Thanks for posting to help others that are struggling with yucky pond water.
I love mine, my pond water is always clear, algae free and perfect water tests. Mine is around 30% plus of my ponds size. I made it large to have the plant room, but the side benefit is it does a great job filtering my pond.
I have a bog filter for my pond, but do not have the sump drain under the pea gravel. We have drained ours twice (to work on pipes), neither time did a bunch of debris come out. We do have piping under the pea gravel that we can open to drain the bog.
I love mine, my pond water is always clear, algae free and perfect water tests. Mine is around 30% plus of my ponds size. I made it large to have the plant room, but the side benefit is it does a great job filtering my pond.
I have a bog filter for my pond, but do not have the sump drain under the pea gravel. We have drained ours twice (to work on pipes), neither time did a bunch of debris come out. We do have piping under the pea gravel that we can open to drain the bog.
j.w
I Love my Goldies
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Great job on that build! Someday I wish to have a bog............don't know if I will ever actually do it tho! Now addy don't bug me about it,lol!
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