Start of construction for 20000gal pool conversion

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I've gone back and forth on various details since my last post, but the basic idea is still the same - upflow bog spilling into the deep end with an intake on the other (shallow) end.
Progress is (slowly) being made on converting my 20000g pool, the foundations for a raised bog have been laid.
PXL_20220825_212928668.jpg

The cinderblock walls will be 4' taller than the concrete pool coping (bog water level will be lower), then covered with EDPM liner and rockwork.

I'm planning to have the liner slightly overhang over the pool edge, could I just build a rockwork waterfall directly over the liner? I figure the other option is building a waterfall wall below the liner, then hiding it with more natural rocks, but I think this would be redundant - the water just has to be directed such that most of it spills over the top of the waterfall. Thoughts?
I'll likely use mortar to hold the rockwork together; I'm thinking the large volume of the pool should be able to handle the relatively small amount of alkaline leaching, but some sealant may be in order.

For the bog's plumbing, I'm thinking of using this 4" perforated pipe, which is meant for underground drainage, but I haven't seen it used in other bog projects (seems most use PVC with holes drilled or cut into it), so I am a little unsure, but it seems like it would be perfect here.
I'm thinking of using a few feet of 2' or 3' culvert for a cleanout vault, to have access to the bottom of the bog in case of sediment buildup. This may be what I use for the pump intake vault as well.

It's somewhat hard to find info on the higher-flow pond pumps, but 2x PerformancePro AP 1-120 pumps are what I'm looking at now, giving 24000gph (minus TDH, of course). Anyone have experience or recommendations here? I threw together a spreadsheet comparing listed specs of a few different high-flow pumps, and this seemed to be the most cost-efficient in the long run, considering the significant power draw of such large pumps. As for the plumbing, I figure I'll have one pump intake for a skimmer (design TBD) and the other somewhat deeper in the pond.

Finally, does anyone have experience with mechanical filtration for a pond of this size? I figure the bog should be sufficient for the biological part, but of course I don't want it clogged with excessive mulm or grit. Right now I'm considering taking a page from the aquaponics guys and constructing a swirl filter of some kind, but I'm not sure if that would be too big to be practical. Ideally, the swirl filter could just be drained and the collected muck could be used as fertilizer. Potential issues I see would be finding a large enough container, but also one that could ideally fit into the existing pump room of the pool. I can't really sink it into the ground easily, not without breaking through several feet of solid concrete or adding a bunch more piping.
Otherwise I think I could go with 'traditional' filter pads, but at this pond size I think they'd have to be huge/or cleaned super often - not too convenient. I don't intend on a large fish load, but there will still be algae, microbes, and debris.

In other news, I found a good source for at least one kind of fish native to my area (important in the unlikely case that this area floods again and invasive fish escape). The Contra Costa Mosquito and Vector Control District, a few counties over with a very helpful biologist who was willing to show me around their stock tanks give me a few Sacramento Perch fry from the ones he was raising.
He also had a several cultures of albino mosquitofish, which might be of interest of to those of you who don't have any chance of them escaping to local waterways.
gambusia01.jpg


Anyway, thanks for reading my rambling, I hope to post more pics as progress continues.
 
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I've gone back and forth on various details since my last post, but the basic idea is still the same - upflow bog spilling into the deep end with an intake on the other (shallow) end.
Progress is (slowly) being made on converting my 20000g pool, the foundations for a raised bog have been laid.View attachment 153635
The cinderblock walls will be 4' taller than the concrete pool coping (bog water level will be lower), then covered with EDPM liner and rockwork.

I'm planning to have the liner slightly overhang over the pool edge, could I just build a rockwork waterfall directly over the liner? I figure the other option is building a waterfall wall below the liner, then hiding it with more natural rocks, but I think this would be redundant - the water just has to be directed such that most of it spills over the top of the waterfall. Thoughts?
The liner will only need to extend below the water line in the pool. I say to this point only as most pools have a good 6 to 8 inch drop from the coping to water line which is ideal no water should be able to splash or wick its way out.

.



It's somewhat hard to find info on the higher-flow pond pumps, but 2x PerformancePro AP 1-120 pumps are what I'm looking at now, giving 24000gph (minus TDH, of course). Anyone have experience or recommendations here? I threw together a spreadsheet comparing listed specs of a few different high-flow pumps, and this seemed to be the most cost-efficient in the long run, considering the significant power draw of such large pumps. As for the plumbing, I figure I'll have one pump intake for a skimmer (design TBD) and the other somewhat deeper in the pond.

Finally, does anyone have experience with mechanical filtration for a pond of this size? I figure the bog should be sufficient for the biological part, but of course I don't want it clogged with excessive mulm or grit. Right now I'm considering taking a page from the aquaponics guys and constructing a swirl filter of some kind, but I'm not sure if that would be too big to be practical. Ideally, the swirl filter could just be drained and the collected muck could be used as fertilizer. Potential issues I see would be finding a large enough container, but also one that could ideally fit into the existing pump room of the pool. I can't really sink it into the ground easily, not without breaking through several feet of solid concrete or adding a bunch more piping.
Otherwise I think I could go with 'traditional' filter pads, but at this pond size I think they'd have to be huge/or cleaned super often - not too convenient. I don't intend on a large fish load, but there will still be algae, microbes, and debris.

In other news, I found a good source for at least one kind of fish native to my area (important in the unlikely case that this area floods again and invasive fish escape). The Contra Costa Mosquito and Vector Control District, a few counties over with a very helpful biologist who was willing to show me around their stock tanks give me a few Sacramento Perch fry from the ones he was raising.
He also had a several cultures of albino mosquitofish, which might be of interest of to those of you who don't have any chance of them escaping to local waterways.
View attachment 153636

Anyway, thanks for reading my rambling, I hope to post more pics as progress continues.

I'll likely use mortar to hold the rockwork together; I'm thinking the large volume of the pool should be able to handle the relatively small amount of alkaline leaching, but some sealant may be in order.
Little worry to the mortar being an issue it should stop any serious leaching before the pond balances out but like you said again 20000 gallon little to worry about.

For the bog's plumbing, I'm thinking of using this 4" perforated pipe, which is meant for underground drainage, but I haven't seen it used in other bog projects (seems most use PVC with holes drilled or cut into it), so I am a little unsure, but it seems like it would be perfect here.
I'm thinking of using a few feet of 2' or 3' culvert for a cleanout vault, to have access to the bottom of the bog in case of sediment buildup. This may be what I use for the pump intake vault as well.
Not a big fan of that drain tile piping you mentioned . It is made to go underground. it is perforated. But they are to large for my liking . Even if you put your own holes in it they need to be a 1/4 minimum imo and gravel can sneak in blocking the pipe . Cutting slits I would not think is advisable as if you cut the band or ridges it will lesson the stability of the pipe greatly.

24 inch culvert is big enough for anything you'll ever need to do in the bog . I have the same

2x PerformancePro AP 1-120 pumps are what I'm looking at now
I have a 12000 performance pro 230 it sucks up the juice. Here in ct we have one of the highest rates in the country. But the pump is self is very quite . Never an issue they have baldore pumps the best in the buis. Imo
But I would try a single 12000 gph pump that size pond the turnover does not need to be as high. Unless you plan on over stocking the pond.
I'd do the 12000 or there abouts and try to incorporate a couple circulation pumps toward the bottom.

Are you going to hook up the main drain ?

Keep splash in mind if your going to have a 4 for drop that is a lot of splash that can travel a good distance.. my guess is 6 feet or more.
I do have a 3 foot drop but it is not a straight drop it bouncesdown rocks. That way it helps take away the energy and help contain the water. More like a steep stream then a waterfal
 
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Not a big fan of that drain tile piping you mentioned . It is made to go underground. it is perforated. But they are to large for my liking . Even if you put your own holes in it they need to be a 1/4 minimum imo and gravel can sneak in blocking the pipe . Cutting slits I would not think is advisable as if you cut the band or ridges it will lesson the stability of the pipe greatly.
Too large as in diameter? They have a 3" diam version as well.
Yeah, the perforations are a bit small, I got a 10ft piece for an indoor pond project and the perforations are only about 1/8" x 7/8", though there a lots of them. Going with the more traditional PVC is doable. Wouldn't 1/4" perforations let some 3/8" pea gravel in? I plan to use a layer of river rocks then egg rock which should keep most of the gravel away from the pipes in the first place though.

I have a 12000 performance pro 230 it sucks up the juice. Here in ct we have one of the highest rates in the country. But the pump is self is very quite . Never an issue they have baldore pumps the best in the buis. Imo
But I would try a single 12000 gph pump that size pond the turnover does not need to be as high. Unless you plan on over stocking the pond.
I'd do the 12000 or there abouts and try to incorporate a couple circulation pumps toward the bottom.
I was thinking of just doing the one pump and seeing how it goes. Part of the reason I'm thinking of two is to get a decent-looking waterfall, but one might work. I don't plan on overstocking the pond, but I am considering a few native trout and they need high flow and dissolved O2. Redundancy is a plus with two pumps, though.

Are you going to hook up the main drain ?
Possibly, depending on the ID of the pipe. I think it's only 1.5" which I worry is too to deal with pond debris, especially since it'll be 8' underwater, so not easy to access. I'd like to have it for the circulation, but if it gets clogged that will defeat the purpose of course.
The frogs that had colonized the dredges of water at the bottom of the pool this spring have mostly left, so I will drain it and take a closer look.

Keep splash in mind if your going to have a 4 for drop that is a lot of splash that can travel a good distance.. my guess is 6 feet or more.
I do have a 3 foot drop but it is not a straight drop it bouncesdown rocks. That way it helps take away the energy and help contain the water. More like a steep stream then a waterfal
Definitely not planning on a completely vertical drop, more of a steep stream like you say.
 
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Too large as in diameter? They have a 3" diam version as well.
Yeah, the perforations are a bit small, I got a 10ft piece for an indoor pond project and the perforations are only about 1/8" x 7/8", though there a lots of them. Going with the more traditional PVC is doable. Wouldn't 1/4" perforations let some 3/8" pea gravel in? I plan to use a layer of river rocks then egg rock which should keep most of the gravel away from the pipes in the first place though.
too large? naaa.... i used a 24 inch culvert as my centipede previously.

You HAVE THE RIGHT IDEA river rock around the pipe will prevent the pea stone from getting in the cuts but i am on the side where i prefer 3/4 river for 3/4 of the thickness and 1/4

I was thinking of just doing the one pump and seeing how it goes. Part of the reason I'm thinking of two is to get a decent-looking waterfall, but one might work. I don't plan on overstocking the pond, but I am considering a few native trout and they need high flow and dissolved O2. Redundancy is a plus with two pumps, though.
those two waterfalls are about 10,000 gph i also have two return jets to the pond taking the remainding estimated 2000 gph for my 12000 gph performace pro

Possibly, depending on the ID of the pipe. I think it's only 1.5" which I worry is too to deal with pond debris, especially since it'll be 8' underwater, so not easy to access. I'd like to have it for the circulation, but if it gets clogged that will defeat the purpose of course.
The frogs that had colonized the dredges of water at the bottom of the pool this spring have mostly left, so I will drain it and take a closer look.
nothing says it has to be suction you can probably slip a fitting on the drains pipe and use it as a return jet but at the bottom of the pond.


 
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I am excited to see your final pond! It makes me want to buy my next house with a pool to convert it to a pond.
I'm starting to wonder if it's really any easier to convert than to just build one anew haha. I guess having such steep walls and depth would be harder with an EDPM liner pond. Definitely not the way to go if you need a more natural pond, hiding the edges would be much harder; I'm not even going to try with this one.

In other news, since most of the frogs have left the bottom dredges of the pond, I fully drained it. I plan to powerwash the remaining residue.
PXL_20220831_002700076.MP.jpg
PXL_20220831_210202711.jpg

Found some strange critters inside.
PXL_20220831_012912262.MP.jpg


A shopvac was useful here, but carrying a sludge-filled one out of a pool is a bit tiring.
I'm interested in seeing how the sludge works as fertilizer...

PXL_20220831_205649866.jpg
PXL_20220831_205657257.jpg




Bottom drain revealed. Inside diameter is ~1.6", so this should be 1 1/2 pipe. The outlet is in the concrete-floor pump room, above the waterline. Gravity drainage is probably impractical here.
PXL_20220831_201547822.jpg

I'm thinking about how to use this. Maybe as a periodic 'pond vacuum', just sucking up the settled waste and diverting it out of the pond as garden fertilizer?
A normal continuously pumped intake might be another option, but if I just pump the waste to a filter anyway, this might be redundant, as I'd still have to remove the waste from the filter. The pump would also probably blend the waste into finer particles, which wouldn't be too good for a mechanical filter.
Lastly, maybe I could pump air through it, though it's pretty big compared to standard airline... Also, with a 10000+gph waterfall I'm not sure if this would really add much more O2 than what's already there.


I disassembled the pool pressure filter; maybe it could be used as a pond mechanical filter with some modifications? It has to be completely split in half to be opened, so it would be a pain to clean filter media if it gets filled often.
PXL_20220828_023829836.jpg
 
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I'm looking at a filter with two pleted cartridges with 2 inch pvc feed and supply line. But your pump has reduced lines down to 5/8 and 3/4 . Regardless of how many hp that pump is it can only do so much with the lines reduced that small . That you would see in an Inflatable kiddie pool . Was to small for a inground pool
 
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Agree that a pump-fed bottom drain on a 1.5" line is probably about worthless for handling debris. If you wanted to convert it for aeration, you could treat the 1.5" line as a sleeve for a smaller diameter hose connected to an air stone. Don't think there's any issues using it as is for air, you'd just need adapters on both ends to get down to sizes that air pumps and diffusers are commonly sold in.
 
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I'm looking at a filter with two pleted cartridges with 2 inch pvc feed and supply line. But your pump has reduced lines down to 5/8 and 3/4 . Regardless of how many hp that pump is it can only do so much with the lines reduced that small . That you would see in an Inflatable kiddie pool . Was to small for a inground pool

The pump in that pic is just a booster pump for the solar pool heating system. The main pool pump is larger with 1.5" lines. In any case, I don't plan on using either of the existing ones.
The pressure filter actually takes 4 pleated cartridges, but they're pretty fine, not really sure if they'd be suitable for continuous 10000+gph flow of pond water. Converting it to a backflushable mechanical filter is another idea I had, but I'm not sure how practical that would be.

Agree that a pump-fed bottom drain on a 1.5" line is probably about worthless for handling debris. If you wanted to convert it for aeration, you could treat the 1.5" line as a sleeve for a smaller diameter hose connected to an air stone. Don't think there's any issues using it as is for air, you'd just need adapters on both ends to get down to sizes that air pumps and diffusers are commonly sold in.
I'm toying with the idea of pumping water into it to agitate any settled debris back into the water column (where it could theoretically be filtered). Maybe with a flat cover to direct the flow outward, along the bottom surface. Kinda like a ceiling vent diffuser, but upside down and with water.
7089-9066189.jpg
 
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even 1.5 is not large enough for 10,000 gph. At best without jacking the psi, 4800 GPH is max for a 2 inch line. two 2" lines can think about the needed volume but they have to be joined together at a 3" even though simple arithmetic would make one think that two 2" lines can carry more volume than could one 3 inch . its actually the reverse the three can carry 3 to 4 times as much volume as a 2" pipe.

The rhino drains do what your referring to they have a air bladder that as the air lifts it pulls debris from the bottom water level and to the drain.

for a pool conversion i'd think about drum filters and a bog or sieve filter and a bog
 
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I read (skimmed pun intended) so I may be mistaken but did not read anything about a skimmer? We have a 20000 pond with a skimmer box and waterfall return. We have tons of tiger salamander babies this year and I had to modify our skimmer with a netting system to catch them before they got sucked into pump. I can post pics later if you need ideas. it works great!
 
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I look forward to seeing your final version! I have a 20,000 Natural Pool, and use a box with many layers of Metalla filter medium then a UV sterilizer with lots of bio media. For me, having a smooth bottom that is easy to vacuum with a Pond Vac has been great.. if you are willing to vacuum the bottom of the pool and dump it into the lawn once in awhile it has worked for me.. I swim and photograph in my pool so clarity is important. I ripped out my old pool because there was gravel everywhere.. and no way to clean it. Now my plants are in pots, and the bottom is liner or rock.
 
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I read (skimmed pun intended) so I may be mistaken but did not read anything about a skimmer? We have a 20000 pond with a skimmer box and waterfall return. We have tons of tiger salamander babies this year and I had to modify our skimmer with a netting system to catch them before they got sucked into pump. I can post pics later if you need ideas. it works great!
Some of the intake volume will be from an intake bay are built into the shallow end (across from the waterfall). There are two existing skimmers in the pool, but one is on the side and the other is behind where the waterfall will be, so they're not really placed ideally. I might se the side skimmer, but we'll see. Might also just get a skimmer box if the intake bay doesn't work well.

I look forward to seeing your final version! I have a 20,000 Natural Pool, and use a box with many layers of Metalla filter medium then a UV sterilizer with lots of bio media. For me, having a smooth bottom that is easy to vacuum with a Pond Vac has been great.. if you are willing to vacuum the bottom of the pool and dump it into the lawn once in awhile it has worked for me.. I swim and photograph in my pool so clarity is important. I ripped out my old pool because there was gravel everywhere.. and no way to clean it. Now my plants are in pots, and the bottom is liner or rock.
I'm planning to keep the deep end pretty much clear for easy cleaning. How often do you need to vacuum it? I wouldn't mind doing that occasionally, but the deep end is 8ft and all the pond vacs seem to say they only lift up to 7.5ft so I'm not sure. I'm thinking of putting a screen over the existing drain and using it to occasionally suck up the fine sludge, and just dumping it straight into the yard, while using a pool net for the bigger leaves and such.
How often do you clean the mechanical filtration, and how do you do it? I want to keep as much suspended solids out of the bog filter as possible, but I'm still thinking about making a mech filter big enough for 20000gal.
I'm probably going to use a radial flow settler before some matal or something similar. A drum filter would probably be easiest, but also really expensive.
 
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Some of the intake volume will be from an intake bay are built into the shallow end (across from the waterfall). There are two existing skimmers in the pool, but one is on the side and the other is behind where the waterfall will be, so they're not really placed ideally. I might se the side skimmer, but we'll see. Might also just get a skimmer box if the intake bay doesn't work well.


I'm planning to keep the deep end pretty much clear for easy cleaning. How often do you need to vacuum it? I wouldn't mind doing that occasionally, but the deep end is 8ft and all the pond vacs seem to say they only lift up to 7.5ft so I'm not sure. I'm thinking of putting a screen over the existing drain and using it to occasionally suck up the fine sludge, and just dumping it straight into the yard, while using a pool net for the bigger leaves and such.
How often do you clean the mechanical filtration, and how do you do it? I want to keep as much suspended solids out of the bog filter as possible, but I'm still thinking about making a mech filter big enough for 20000gal.
I'm probably going to use a radial flow settler before some matal or something similar. A drum filter would probably be easiest, but also really expensive.
 
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I can feed this filter from a surface skimmer as well as a deep intake.. It has a 1.5” drain in the bottom that I dont use- the easiest way is to slide the pond vacuum between the filter layers and send the muck in to the yard..and it only needs to be done once a year or so. My pond vac loses some power (suction) at the bottom app. 7 feet, but it still works. My opinion is never send muck into your filter.. dump it in the yard if you can
 

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