Help - Build starts next week, bottom drain pipe size?

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Hi all,


I would like to pick your brains again. I'm just about to start building a pond (in the next week) and I need your advice on pipe sizes for bottom drains and intake bay filters (Skimmers).

Pond stuff layout.png

Here is a model of the pond, as you can see as well as bottom drains and intake bay filters it uses a bog filter with a water reservoir [settlement chamber] underneath it. I'm also going to build a “strainer box” to remove all the larger debris, leaves etc. from the bottom drains. (It's just a plastic box with a very large mesh basket, the top of the box will be left open, with the water level the same as the pond)

schematic v3.png


I know conventional wisdom says 4” pipes for bottom drains, but I'm concerned I will not have enough flow to keep the pipes clean. I want the pond to be minimal maintenance hence the use of the bog, so I don't want to purge the pipes to keep them clean all the while.


Some facts and figures, I normally use metric but I will put it all in US imperial.

  • Overall volume of pond and bog: 7380gl
  • Pond: 5570gl
  • Reservoir: 660gl
  • Bog only: 1150gl

If I take total volume of waters as Pond + Reservoir = 6230 gl + ¼ of bog, say 6500 gl in total.

So, to change the water ever hour we need a flow rate of 6500 gph

I understand the sensible minimum flow rate for a 4” pipe is around 3600gph.


So, it appears I do not have enough flow rate to support 2 x 4” bottom drains and the 2 intakes bays. I've have two intake bays as I don't really know where surface debris will build up, and it's easier to build them now than in the future.


To keep flow rates up to keep pipes clean should I reduce the sizes of pipe? Or just have one bottom drain?

One other thing, even though it's using bottom drains, I guess this should be thought of as a pump fed pond.

Thank you for any advice.
 
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Where is the house and where is the siting area i know its not what you asked but youll see why i ask in a minute.
 
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Where is the house and where is the siting area i know its not what you asked but youll see why i ask in a minute.
This is the back of the house, so there may be chairs on the raised area, but we intend make out door kitchen under the pergola and there will also be seating this side of the pond. This image doesn't really show it, but we hope there will be lots of plants ground along side and aorund the pond and of course in the bog.

Screenshot 2024-02-28 004530.png
 
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First thought is skimmers in the corner i don't think they work as well as you think. . LOOK IT this way , water likes to flow and like a water closet the water rotates in a circle, you have a large round wall but where are your return jets.? return jets are invaluable making your pond circulate and have direction. pushing leaves and dust to the skimmers before they sink. I had placed my skimmer up by the falls as action reaction so as new water came in and pushed across the pond the surface water on the side rushed toward the source the waterfall .

The settling chamber should be that a large are for the water to enter and have enough space to settle out anything floating in it. often ponds like your will do brushes in this area and make the water go up and over brushes then go under and over again.

i'd put both pumps side by side to the left up against the wall in the picture but at least a foot and a half off of it for maintenance and make the back half of that area one large settling area.

I have 3" on my drain lines and even with a second opening on the pipe the first opening closest to the pump 12000 was too strong and sucked a fish or two to the floor and held them there . One thing is for sure you will want gate or ball valves on EVERY line.

you have the lines emptying under the mats in the settlement . wouldn't it work best to over size the area and have the pump pull the water through the mats ? if worried about blockage make your self an over flow pipe that comes up above the mats and above the water line so if it did back up it has like a 4 inch pipe to drop down . untill the mats get cleaned. also if the debris falls on top you can use a net to spot clean them.

The reason so many on your side of the pond go with 4" is they use the 4" as a gravity draw no pump just flow. when there is no psi you need larger pipe. If your heading for a rdf some day the 4" is preferable but i can't see where 2 three in lines from the floor and 2 two inch from the intakes would not be more than enough to supply a rdf for a 7000 gallon pond

Imo the return water should take as long as possible to reach the returns. one of your drains is rather close to the falls . if the water fall drops into the pond it will mix in that area and push out . thats where the one drain in particular is too close imo . I prefer making the water rotate in one direction and circulate the pond making a vortex per say

i would also not throw 6000 gph at the bog i'd do 4000 tops and take the other 2 and make return jets for some circulation pushing water toward your skimmers. one probably off to the left in the corner pushing toward the skimmer on the left and a second on the right of the falls pushing toward the other skimmer this will make a the water circulate back toward the falls in the middle from the skimmers and that should be dropping so the drains in the pond then pick that up.

i know you mentioned rhino drains just keep in mind you don't see much when they are in the viewing area the ripples and bubbles distort a lot
 
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SLOPE THE BOTTOM TOWARD THE HOUSE .
push the drains back toward the house the one drain on the lef closer to the corner on the left close to the house
the two intakes closer together pulling all the water in one direction. hopefully these are in a courner that your wind blows toward and not from the skimmers toward the waterfall.
return jets pushing water toward the skimmers that have directional jets.

This is more what i would do but there realy is no right or wrong i have not built a raised pond such as your before but this is more my take to have only 600 pulling in two completely different directs doesn't compute to this yankee.

blue arrows would be presumed flow direction
red arrows are directional flow jets
black are the drains but again if they are running with air all the time will this kill the view . i put in a rhino and never use it i cqan't see my fish
 
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actualy if you are using on with koi toilets that changes ceverything . are you using those?
 
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Looking at the design some more you have your pumps Pulling water. Pumps push water real well but only moderately pull water. With your lines coming up above the water level this could fail and not work at all. If you can have the water reach the pumps by gravity then it will work
 
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Looking at the design some more you have your pumps Pulling water. Pumps push water real well but only moderately pull water. With your lines coming up above the water level this could fail and not work at all. If you can have the water reach the pumps by gravity then it will work
The pipes to the pumps never go above the water level, even through strainer box, they well below the pond water level.

1709124875419.png

1709124974043.png
 
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SLOPE THE BOTTOM TOWARD THE HOUSE .
push the drains back toward the house the one drain on the lef closer to the corner on the left close to the house
the two intakes closer together pulling all the water in one direction. hopefully these are in a courner that your wind blows toward and not from the skimmers toward the waterfall.
return jets pushing water toward the skimmers that have directional jets.

This is more what i would do but there realy is no right or wrong i have not built a raised pond such as your before but this is more my take to have only 600 pulling in two completely different directs doesn't compute to this yankee.

blue arrows would be presumed flow direction
red arrows are directional flow jets
black are the drains but again if they are running with air all the time will this kill the view . i put in a rhino and never use it i cqan't see my fish
I can move the drains to the house, the pond bottom will be graded to the the drains.

Unfortunately the wind comes in from the top right.

pond flow.png


So my feeling is surface debris will gather at the top left of the pond. We could also get debris in the top left as well, from eddies as the water surface will be below the edge wall level.

To prevent stuff gathering behind the waterfall and to bottom left corner, I could add a water jet as shown in red. I can divert some of the skimmer pump water.
 
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you have the lines emptying under the mats in the settlement . wouldn't it work best to over size the area and have the pump pull the water through the mats ? if worried about blockage make your self an over flow pipe that comes up above the mats and above the water line so if it did back up it has like a 4 inch pipe to drop down . untill the mats get cleaned. also if the debris falls on top you can use a net to spot clean them.
It looks like there may be confusion again. The bog area is designed like a typical Aquascape Wetland Filter, with water being fed into centipedes under the plastic crates (AquaBlox Water Storage Modules) and making up through the water reservoir the percolating up through the various grades of gravel.

There are no mats in this area, the only way to clean it is to drop a sump pump down the inspection chamber(snorkel) and pump it out. This will be done a few times a year

I can increase the depth of the water reservoir to take up to about 1000gl. I don’t really want to increase the area of it.

If there is going to be too much build of debris in the bottom of the water reservoir, I will have to use a pre-filter before it goes into it, the rdf as originally discussed.



So to sum up.

  1. Move bottom drains nearer to house and ensure pond bottom slopes down to them.
  2. The skimmers are currently in my best guess locations to where the surface debris will go.
  3. I will add a jet in near waterfall and push debris away from corner and from the back of waterfall to the far skimmer
  4. All pipework from bottom drains and skimmers stays below pond water surface level.
  5. I will use 3” pipe on Bottom drains and 2” from skimmers
  6. All pipes will have either ball or gate values, to allow control of water flow and isolation of pumps etc
  7. I will also try get variable rate pumps to control flow
For me the area of concern is the “settlement chamber” will it clog up with debris too quickly. it is as Aquascape would say a water storage, so mats.

  • 8. I can increase the depth of water reservoir under bog say from 400mm to 600mm, this will take it upto 1000gl, would this help?
  • 9. Or do I put in a rdf to remove major debris before the bog area?, currently I have my strainer to remove very large debris
I think that's all the main points.

Thanks for all of the input
 
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are you planning to make your bottom drains have air ? if you they really cut down on the view of the fish. i know they work well as koi toilets but they also kill the view and they do divert water flow. above and below the surface a good thing if taken into account. i think id go with them but make a switch somewhere so it cab be controlled or shut down when desired.
I wonder if a wall of air coming up along the rounded wall would be appealing youll have air and view but no toilet

what i was referring to was the bottom drain strainer bellow not the settlement chamber of the bog. if the drain empties on top of "i assumed
will have to use a pre-filter before it goes into it, the rdf as originally discussed
That return from the rdf could be your return jet for circulation

matts "you can spot clean them when needed with just a net have the pumps intake be at the bottom drains empty on top. "

what is the grid in the bottom drain strainer area that was what i suggested making larger
  1. Move bottom drains nearer to house and ensure pond bottom slopes down to them. if no air that will be the best spot to delay filtered water from being pulled back into the filter too soon.
  2. The skimmers are currently in my best guess locations to where the surface debris will go. I think if you look at prefab ponds the skimmers might be close to the corners but not in them.
  3. I will add a jet in near waterfall and push debris away from corner and from the back of waterfall to the far skimmer might want one down low too
  4. All pipework from bottom drains and skimmers stays below pond water surface level. thumbs up are double ball valves or check valve and ball valve a good idea if one ball valve fails how much water will you need to drain
  5. I will use 3” pipe on Bottom drains and 2” from skimmers i wonder if you can put a reducer in the three inch if you leave threaded in the drain housing so if 3 is to big you can just screw in a reducer
  6. All pipes will have either ball or gate values, to allow control of water flow and isolation of pumps etc
  7. I will also try get variable rate pumps to control flow
i mentioned before someone with a raised pond that i know when he shuts down for winter he didn't think how air would get in the pond and has airline tubes going up over the sides a over site he hates
For me the area of concern is the “settlement chamber” will it clog up with debris too quickly. it is as Aquascape would say a water storage, so mats.
thats why i sugested making the biottom drain strainer compartment much larger and if it falls on top you can have a over flow so if it starts to clog it raises and finds the open pipe to the bottom where the pump will be
  • 8. I can increase the depth of water reservoir under bog say from 400mm to 600mm, this will take it up to 1000gl, would this help? the large the amount of gallons the less likely to have any accidents from ammonia spikes lack of oxygen etc but bif you need to treat for parasites it will cost more.
  • 9. Or do I put in a rdf to remove major debris before the bog area?, currently I have my strainer to remove very large debris the prefilter on the skimmers and the bottom drains is plenty for the bog . the rdf is more a polisher a rdf is mechanical like is a bog but as far as clarity with one major difference the bog does not remove the debris it breaks it down . the rdf removes it but has no biological filter unlike the bog that is one giant bio filter
 
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The format of these threads gets very confusing, but I think I'm getting with help.
I wonder if a wall of air coming up along the rounded wall would be appealing youll have air and view but no toilet

It sounds a good idea, I will look into it.

what i was referring to was the bottom drain strainer bellow not the settlement chamber of the bog. if the drain empties on top of "i assumed

That explains my confusion. I could make the strainer box bigger, I'm actually going use a striped down wheelie bin (the cheapest way of getting a strong plastic box ), they are pretty large. With a mesh basket and some course filter material and yes the pump will pull the water through any filter material. I like the the idea of a simple overflow pipe into the pond.

thanks for the help I do have a few more items to think about. I'll put them in another post.
 
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The format of these threads gets very confusing, but I think I'm getting with help.


It sounds a good idea, I will look into it.



That explains my confusion. I could make the strainer box bigger, I'm actually going use a striped down wheelie bin (the cheapest way of getting a strong plastic box ), they are pretty large. With a mesh basket and some course filter material and yes the pump will pull the water through any filter material. I like the the idea of a simple overflow pipe into the pond.

thanks for the help I do have a few more items to think about. I'll put them in another post.
I'LL start typing up the invoice
 
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We are getting there. there are still some questions going round in my mind.

  1. The BDs goes through the strainer box and then gets pumped into the bog. I was looking at putting a non return valves between the pumps and the bog, is this the best place? I will also look at putting anti syphon pipes in the bog just in case something goes wrong
  2. The majority of pumps in the 3000gph range have smaller connectors, so I presume from the strainer box to the pump and then bog it will be ok to use the pipe the same size as inlet on the pump? probably 2"?
  3. As a fail safe i need to think of a method to purge the bottom drains and skimmer pipes, not sure how to do that yet?
  4. Is there anything else i should be thinking about?
 

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