Help! I don't know what I'm doing! (Large pond with bog)

[lifeisgoodtoday]

I hope this doesn't get too long. Here are my main questions, before I write a bunch of details:
- Can you have a pond that is too big for bog filtration because the amount of gph needed to circulate means that the flow through the bog would be too fast?
- Do I really need special tubing that is $8.99 per foot to run from my pump to the bog and then create the manifold that goes under the bog?

A little background - we have a natural water retention area in my yard that we intended to dig out and turn into a rain garden, and somehow (thanks Pinterest!) that turned into wanting a pond. So we had the owner of a local pond store come out and look at the area and make some recommendations, the gist of which was a large pond with bog filtration. He drew a diagram of a 60x75ft pond and 20x20 ft bog, which we ended up sizing down a great deal and leaving an area for excess rain water collection. The area is now roughly dug out and graded.

The pond is an oval, about 20ft x 35ft, sloping gradually down to 5ft deep in the middle, and an estimated average depth of 2-2.5 ft. I calculated it at about 13,000 gallons. Above the water line of the pond we will have an extra stone covered area, about 12 inches wide to hold any rain water drainage (capable of holding an extra 5000 or so gallons as needed). The bog area then wraps around that stone area in a crescent shape and is planned to be around 300 sq ft. Water level of the bog will be about 2.5 ft above the pond water level, not including any rain water.

And here is where my questions start. On Friday when we went to buy the pump, the pond store people told me and my husband that the pond was too big for the entire volume of the pond water to filter through the bog at once - that it would basically be flowing too fast and the plants wouldn't have time to suck up the nutrients. They recommended a 9000 gph pump for the pond volume, but said we would only want to send about 2000 gph to the bog while the remainder of the water is diverted back into the pond. They recommended creating a manifold with a ball valve (I think) for this diversion. I have googled but I can't find anything that describes a similar set up, or warns that some pond volumes are too big for bog filtration. So any feedback on this idea would be really helpful!

My second question - at the store they recommended 3 inch wide tubing/flexible piping to run from the pump to the bog, and to use for the bog system, by cutting slits in it and spiraling it around the bog. First of all, this tubing is so stinking thick that I can't imagine that it will be flexible enough to create the spiral needed. 2nd, they calculated about 115 ft of tubing needed - over $1000! That's more than the pump cost. I'll pay it if necessary, but I read a lot about people using a special kind of PVC. Does it cost that much too?

Thanks for any thoughts!

 

[Jhn]

Welcome, sounds Like you are going to have a nice size pond. Pics of what your doing will help us, see exactly what you are trying to do.

First off, no there is no such thing as a pond being to large for bog filtration. The general rule is to shoot for the bog surface area to be about 30% of the pond surface area, which yours is more than that. You can’t push all your pumps water through the bog, but it doesn’t need to be to filter your entire pond.

A 9000 gph pump is way undersized for your pond, I would get at least 15000gph pump. I would try to turn you pond volume over at least once per hour( most shoot for 1.5-2x). The pond store is correct that you don’t want to much flow through the bog, so the plants have contact time with the nutrient laden water. You can as they suggested put a Y in the line with a valve and send less water to the bog and more to a waterfall area or have 2 pumps in your pond one to feed the bog say a 3000 gph pump and a 10-12000 gph pump feeding a waterfall or stream returning to the pond. Either way a bog will be all the filtration your pond needs.

No you don’t need to use flex pvc the more expensive hose in the bog....Most use 2-3” schedule 40 pipe with slots cut in it every few inches, creating a grid under the pea gravel, just put clean out pipes at the end of each line buried in the gravel.

@addy1 has a thread stickied at the top of this forum (pond construction) on how to build an upflow bog.

Many of use on here have ponds roughly the size of yours, filtered with nothing but a bog and have been doing so for years. If you do some searches myself, @addy1, @poconojoe, @GBBUDD, @Lisak1, have bogs of varying designs and complexity that work great in our ponds. All of us have build threads on here as well describing how we built it with pic....

 

[poconojoe]

You are wise for starting out with bog filtration. Many of us struggled with inadequate costly commercially bought filters and UV lights only to remove them and convert to a bog. So much time and money wasted.

I prefer flex PVC for its durability. I got tired of replacing that corregated "pond hose" every couple of years. That stuff is garbage and not cheap. Flex pvc will be the last hose you will ever buy. You will be saving long term. I bought a 25 foot roll of 1-1/2" black flex pvc from Amazon for $50. Some members here have had great results with sump pump hose, which is less costly and way more durable than that corregated "pond hose".

Within your bog you won't be using any hose. It will have to be solid ridgid schedule 40 PVC pipe. Just think of all that weight of the pea gravel and you'll understand why it needs to be schedule 40 ridgid PVC. Your flexible hose will come from your pump and change over to ridgid PVC when it gets to the bog.
The solid schedule 40 pvc manifold under the gravel should have slits cut 1/3 down through the diameter. I cut mine with a sawzall. Some people use a circular saw or a cut-off wheel on a grinder. The slits need to be narrow enough so the pea gravel doesn't block them or fall inside, but wide enough not to hinder water flow. I spaced my slits 1-1/2" apart.
Some people face the slits down, some up. It seems to be a matter of opinion. I faced mine up, thinking it would have a lower tendency for clogging if there's any buildup of muck.

At the end of your manifold pipes the solid pvc gets turned upward and ends slightly above the gravel. There you have a screw-on cap. This is your clean-out stack. You can run your pump with that open to force out any buildup of muck in the manifold.

The bog surface area should be 30% of the pond surface area.

As suggested, you can use more than one pump in your pond or you can split the output of a pump and use valves to regulate the flow to each output. You don't want the water to flow too quickly through the bog.

Here's my bog thread:
https://www.gardenpondforum.com/threads/my-add-on-bog-build.26848/

And addy's bog showcase:

Bog building, also called upflow filter, eco filter, wetland filter

I was asked to start a thread on how to build a bog. This is my rendition on bog building 101............. Building a bog: Before you decide to build a bog, you need to know what you want its primary purpose to be. Total pond filtration bog filtration combined with another filter. If you...

www.gardenpondforum.com

 

[poconojoe]

Oh, I have all my pipes, hoses and pumps within the pond/bog. None are outside of the pond/bog. So in case there's a leak I won't lose any water.

 

[addy1]

I filter around 10-11000 gallons (8 ponds in loops from large to small) with a large bog and a pump rated at 6800 (not removing head pressure) All except for a small amount of the pump flow goes into the bog. It filters the ponds without issue. I have a garden hose split off the feed of the bog on a slow flow going to a few small ponds that waterfall back into the big pond. It creates a good flow though the bog, waterfalls back into the pond.

I have shubunkins, no koi, and plants in the ponds.

 

[Mmathis]

Hello and welcome!

As already stated, no size limits, and use 2” (or whatever size....) PVC pipe, and make a “manifold” system for under the gravel of the bog.

Maybe, read through some of the bog builds on here, and get an idea of what your possibilities are. There is no “one way” to do a bog, though their are right ways, and not-so-right ways (IOW, effective, vs not effective for the purpose of the bog).

I have no idea about the pump size and how much and how fast to flow through the bog. It seems like you could split the pump with some water going through the bog, and some water going through a biological filter (or an aerating fountain — your pond is big enough). I did that (Split the water), but my situation is unique. I’m sure you’ll get good advice!

My advice has always been to do your research ahead of time, and learn ALL you can from the start. Then, once you understand WHY things happen the way they do, and WHAT is going on, you will be in a better place as to decision-making. What is it they say in carpentry, “measure twice, and cut once?” I like to learn all I can, then I feel empowered enough to ASK QUESTIONS, and TO QUESTION something — and not just do it because someone else said so, or that’s the way it’s always been done.

 

[j.w]

@lifeisgoodtoday

 

[combatwombat]

You don't have to use flex pvc to get from the pump to the bog. Very expensive, especially if it's a long distance w/ big pipe. You can go with rigid PVC for a fraction of the cost, just a bit more difficult to run since you can't bend it much and you need more fittings. Look for the 20' sticks w/ bell ends if you really need to go a long way.

Also, the bigger the pipe in your bog, the slower the water will move through it, which is what you want.

 

[GBBUDD]

Can you have a pond that is too big for bog filtration because the amount of gph needed to circulate means that the flow through the bog would be too fast?

Absolutely unless your la la la loaded....

Google million dollar back yard view on you tube

Do I really need special tubing that is $8.99 per foot to run from my pump to the bog and then create the manifold that goes under the bog?

no you do not if you live in an area with no winters soft soils pvc sceduel 40 all the way

They recommended a 9000 gph pump for the pond volume, but said we would only want to send about 2000 gph to the bog while the remainder of the water is diverted back into the pond. They recommended creating a manifold with a ball valve (I think) for this diversion. I have googled but I can't find anything that describes a similar set up, or warns that some pond volumes are too big for bog filtration. So any feedback on this idea would be really helpful

You have very similar build to mine . The link is in blue below this text. I use a 12000 gph performance pro pump and I split the return and the suctionmy bog is a minimum of 6 feet 7 on one end where I used 24 inch double walled plastic culvert pipe. I cut slots at what would be 10 and 2 o'clock and pumped in the end where the 2 inch feed pipe is aimed at the wall where it enters the culvert this way any debris is pushed out of the end of the pipe and the water flow is lessened and only slow displacement is pushed only by slow displacement in the large culvert. So the heavy sedimrnt is allowed to fall out of the water column but stays in the pipe because the pipe is solid fro 2 o'clock to 10. It then goes through 4 to 6 inch rock to where it is leveled off to a layer of aqua blocks where again sediment is allowed to sit without flow. Then as it is displaced it travels up through 2 inch rock about 4 inches and then a foot of 3/4 and mixed 3/8 " river rock where the plant roots absorb the phosphates nitrates and any other remains elements. Now the other thing I have adopted is in sewer systems that have heavy loads they are now pumping air into the system n s this promotes bacteria to THRIVE all this dead space allows for bacteria to grow on the rocks. Well with the snorkel with a air bladder pumping air in the pipe gives the bacteria all the o2 it could ever need tge result is crystal clear water. Now some of my videos look a little Markey but thats general due to spawning or myself working on the pond. I can't say enough in the indorcement of bogs three pipes return to the pump one 2 inch is from the skimmer one 3 inch is from the main drain. One 2 inch is from negative edge. All with shut off valves to regulate there flow. Then there is three return pipes one 2 inch feeds two return jets creating motion circulation to two heads in the pond. And one 3 inch splits and one 2 inch goes to the snorkel bog while the other goes to a pea stone bog.

 

[Lisak1]

Welcome @lifeisgoodtoday to the GPF and to pond ownership! You've found the right place to come with your questions - lots of experience and knowledge here, as well as people who are happy to share! You've already gotten some great advice, so I won't repeat that. I will just add two pieces for you to hang on to:

1. The people commenting here live with ponds that are bog filtered - can anyone at the pond store say the same? Plus, they suggested you build your bog with flex PVC - not necessary and not something I've ever even seen someone attempt. Have they ever built a bog or even seen one built?
2. You told them you had a 15,000 gallon pond and they recommended a too small pump and, if that price is right that you quoted, way overpriced that flex PVC - I'd be questioning their advice from that moment on.

If you'd like to see a REALLY big pond that is 100% bog filtered, check out this video. This is the feature pond at Aquascape. I've visited this pond countless times and I can assure you it is crystal clear all the time.