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You may not need 4” Bottom Drains & 4" Pipe on your Koi Pond 👍😊
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- เผยแพร่เมื่อ 9 มี.ค. 2022
- In this video, we demonstrate why you do not need to use 4" bottom drains and 4" pipework on your pond or koi pond. We show the different flow rates of connecting pipework between your bottom drain and your filter system.
The main problem with 4" pipe is that people rarely have the correct flow rate so you will always get a build-up of debris which will lead to a blocked pipe.
Multiple 2" and 3" bottom drains will generally suit the majority of ponds however there seems to be a misconception that bigger is better. It certainly is not the case when it comes to flow rate.
Please note the flow rates are really based if your filter system is next to your pond. You will need to allow for a drop in flow for pipe distance, bends & friction. You could allow 15% as a guide. Recommend to plan your job using the minimum amount of bends possible.
For more information on where we obtained our information on flow rates, please visit this link below:
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![Koi Pond Filters - Gravity fed vs Pump fed [which is best?]](http://i.ytimg.com/vi/xM2s6B9AcSI/mqdefault.jpg)
![Koi Pond Filters - Gravity fed vs Pump fed [which is best?]](/img/tr.png)
At college we were taught that it was bad practice to use bottom drains to feed filters. Midwater outlets feed the filter and the bottom drain feeds to waste. Hence the name, bottom Drain, not bottom feed. Great video
Fantastic video I’m currently building a pond around 4100L. Everyone telling me to put a 4” drain but I’ve said I’ve got a 2” bottom drain and I get a look of disbelief! This video really helped me to trust in what I’m doing. Cheers 👍🏻
Thanks for comment. Bare in mind distance etc and bends for friction. Short distance with low amounts of bends 2” fine. Cheer
As per usual your description is spot on & a lot of ponds have oversized pipework that causes problems due to low flow rate. This is also made worse by the fact that the pumps actually put out a lot less than it says on the tin because the manufacturers want the figures to be as impressive as possible. When they quote a pump as having, for example, a 20,000 ltr per hr output, that is when it is taking water from a tank at the side & discharging it from the outlet with nothing attached. No-one has a pond like that so when you add some pipework & lift the water some distance ( the head), then all of a sudden the "20,000 ltr pump is not putting out anywhere near that amount of flow. Very few pump makers give out true flow rates for a given head but as an example when I checked my 13,000 ltr / hr pump lifting the water 1 meter it was actually shifting about 9,000 ltrs/ hr. If I increased the lift the flow rate would decrease accordingly so by the time I get to 3 meters of lift it would probably be little more that a dribble. Head is calculated by measuring the vertical distance from the top of the supply (pond perhaps) to the point of discharge ( filter perhaps), the location of the pump is irrelevant. If the level of the supply goes down, then this increases the head & decreases flowrate. For long runs and / or lots of bends there are friction losses to take into account.
Cheers many thanks
Agreed but what I don't understand is if the flow rate through 4 inch pipe is so fast comes out through the side of the pond wall around half way has a minty degree bend at the bottom of the pond then another minty through side wall then a third one into the drum it can't keep up the flow into the drum with a twenty thousand litres per hour pump pulling from clean side of the drum. The drum flows up to 25000 litres per hour. We get draw down on the dirty side never mind the clean side. It takes a second four inch entry from the skimmer to keep up the flow. If I switched to smaller pipe work I never get enough flow. Which seams to go against what this video is telling us. As an aside the pump after pulling from the drum is lifting that water one meter to the bio chambers and that means it is not even pulling it's rated 20000 litres per hour so there really should not be any draw down in drum on the dirty side the pipe work under gravity should easily be able to keep up even accounting for the three nineties the water has to flow around . I am speaking from practical experience this how my pond is filtered and the maths shown does not equate to what is actually happening. Perhaps he could do a video on loses due to pipe bends to reflect what I am seeing.
@@gregorygreg4263 So you have a drum filter which is being fed by gravity from the pond using 4 inch pipework but the flow is poor. The most likely problem here is that there is not enough difference between the pond water level & the water level at the discharge in the drum filter. The greater this difference is, then the greater the flow will be. Any losses due to pipework, bends etc will be virtually zero so this is not a factor. Likewise the routing of the pipes, where it exits the pond etc etc, does not matter. The easy way to check the difference is to keep getting rid of the water coming out of the pipe in the drum filter whilst lowering the level in the pond. When there is no more flow the 2 are level & you can measure the amount the level has dropped in the pond. In your case you will probably find this is a small amount & therefore not sufficient. The solution is not easy as there are basically 2 options. Either raise the water level in the pond or lower the level of discharge into the drum filter ( by digging a pit to sink the filter into) so there is a bigger difference to create more flow. Otherwise it would be a complete redesign pumping directly out of the pond. Good luck.
I normally agree with the Pondman on most topics, but this one is misleading. I do agree that bottom drain pipework will require a strong purge and/or be designed for rodding. However to take for example the 3in drain that can flow at 8.4kGPH without pressure is rubbish. Water only flows in pipes under pressure. In this case the pressure is created by gravity head. Using a recognised gravity flow chart, that particular flow rate would require at least a 10in drop from pond to first chamber. If subsequent chambers were similarly connected, in say a three barrel system, the last pump containing barrel would be sucking air!
Thanks for comment. It’s not misleading, we are always factual. If your pump pumps faster than the water moving through your pipework to fill the “void” the pump has left, then you will need thicker pipework. If it can’t pump faster then have have larger diameter pipe is just a waste of money.
@@thep0ndman Maybe we are discussing semantics here, but you stated that these maximum flow rates required little pressure. A 10in drop from say one barrel to another is significant in this context.
That was a really interesting video, really opened my eyes to the drawback of using 4” pipes🤔. Unfortunately my pond is already built……with a 4” drain but I did build in a rodding pipe and have been purging it every couple of months so hopefully my maintenance regime is sufficient 🤞👍. Just started watching your back catalogue so thank you as there is a lot of useful information in 5hem👍🐟🈲😊
Thanks for the reply! At least you can get to it and maintain it. TBF the ponds we get called out too generally are the ones which have not been looked after properly. We never get to see the nice ones 😭😀
Further to the previous comments about pump output I have managed to get a graph for the Evolution Aqua varipumps & as an example the 20,000 ltr / hr puts out around 16,000 when lifting 1 metre, 12,000 ltrs @ 2 metre , 11,000 @ 2.5 metres & 10,000 @ 3 meters head. That is before losses in pipework are taken into account.
Cheers
I have used 2 x 2” pipes for a fry grow on and i don’t get the draw needed to feed the 15k pump. I learnt a key design consideration is the length of the pipe and how many bends you have in it. There is huge friction loss in 2” pipes compared to 4”, especially if you have 90 bends to allow retro fit bottom drains and skimmers. I now always use the plastic pipe shop calculator to try and ensure I get enough flow to the pump.
Thanks for the reply Paul. Would be interested to see the setup. Feel free if you get time to send some pics to info@simplypondz.co.uk if you ever get a spare mo cheers
The plastic pipe shop are also extremely helpful
Im in the planning fase and my pond wil be around 25.000 liter. I want to put in a vario pump with max capacity of 30.000 liter/hour. Would a 4 inch amd 2 inch bottom drain be wise. (4 inch on the far end)
Thank you for this video
Excellent info 👌😎
Glad it was helpful!
I use a 2 inch bottom drain and pipes in a 30000 litre
Pond this is a low pressure
System and it allows the
Filter to work as designed
Glad it’s working well for you, send us a picture?
Hi, interesting video, my pond is 20 years old 3000 ish gallons single bottom drain 10,000 litre pump from multibay. The only time it has blocked was when the dome came off of the drain and the dogs toy followed by blanket weed got into the pipework. the connection onto the multibay is by a tee not an elbow so i can rod the vertical pipe and create vacuum sucking the crap out. I do this every 3 months or so just for the hell of it. Keep up the good work, what area's do you cover? 🤓
Well we certainly have never pulled out a dog top from a bottom drain that is quite impressive! 😀 TBH we usually come across blocked drains with leaves and blanket weed so I guess it can also depend on where your live in regards to trees and if you take care in maintenance ie treating for blanket weed etc or removing leaves as and when. We cover Sussex, Surrey & Hampshire!
I fit 4 inc bottom drains on ever pond I build never have a problem think you should like to the pro pond builder
Yes 4”’bottom drain are worth having with the correct flow rate and pond size couldn’t agree more
@@thep0ndman when I have moro time to do video I show you pond I'm doing now gone 7000galons on 4inc drains how they should be set up mabey ever one can help people in the right away as I hate doing things twis happy ponding
@@jpwatergardens2290 no problem. Yes like said before always up for 4inch drains as long as people have the correct flow rates. We have unblocked quite a few so only speaking from actual people who did get the flow rate correct. keep up the good work
I'm building a 10000litre pond with a multibay filter that recommend a flow of 6000litre per hour . What size pipe / bottom drain would you recommend ?
Thanks for the comment. It can depend on how many bends and distance from the bottom drain to your filter if you were to choose 2inch drain because of friction. The closer the better. Or you could use a 3” to be safe if you have a few bends and distance is further away. Defo you won’t need 4”
Interesting. More interesting is if your insurance provider sees this. Thanks for the info
Thanks for comment but not sure what you mean cheers
@thep0ndman
I've mentioned these theories on forums as I try to decide on my pipeline and the claims made here have been rebuffed by everyone. I'm not saying I disbelieve, just what others have said. I have 9000lph submersible pump with settling bay and diy sieve before it. Very short run for pipes as filters will be beside pond. 11000 litre pond approx, also running 8000lph pump for skimmer. What's my best bet? Literally everyone is screaming 4" and I'm confused how advice can differ so much.
Hi mate for some strange reason the koi industry just follow everybody else, regardless to if it makes sense or not. 4” of water is massive so unless your pump is large enough to generate enough pull to prevent settlement, 3” is plenty and loads cheaper. It really is t rocket science people are just bias because they have already installed a 4” they say everybody else should and it’s the correct thing to do. It is if you use very large pumps. Who wants settlement and purging is just a waste of time
@@thep0ndman thank you for your response, what you say really makes sense. I love your no nonsense approach. I'm also committing another heracy by planning a wetland bio filter to compliment my diy settlement chamber and diy sieve
I can only say I have a four inch bottom drain up side down on the bottom of my pond the dome part being left out and the gap created by the ring with a gap all around you can put your little finger in . I have a four inch Skinner as well both go through the side wall of the pond and both are under gravity into the drum filter which has a maximum flow rate of 25000 liters an hour. If I run my 20000 liter an hour pump at maximum flow which is pulling from the clean side of the drum and rising up a meter to two three hundred litres bio chambers connected in series and then dropping under gravity back into the pond. Pipework to the bio filters is 2inch and four inch dropping into the pond. If you shut the skimmer off the drum float drops and the drum starts cleaning. The system can only handle the pump running at around 80% and allow you to shut off the skimmer. If flow rates are so good through four in pipe I should not have any problems with the drum being kept full when I shut off the skimmer with the pump running at 100% because all pipe work should be able to handle the flow but it appears the four inch bottom drain can't keep up the the amount the pump can pull from the drum.
Hi thnx for the comment. 25k lphr is pretty slow for 4” pipework.
I would also like to say that if 1.5iinch pipe can handle 9500 liters per hour why can't my kitchen sink cope with the cold water tap draining instead it starts to fill up if the tap is running wide open. I am sure I don't get that much water coming into my house.
I should not see any draw down on the dirty side of my drum filter if my pump can only pull 20000 litres per hour when fed by two 4 inch pipes as said earlier one bottom drain and a skimmer. This should easily cope with the pull of the pump. If I used smaller pipe I think my drum would be cleaning continuously as the float would drop even further with the draw down.
Your sink is blocked thnx for the comment
Cloud you show how the 14400 GPH under no pressure or gravity is calculated? Since, I see different numbers from different source.
Thanks for the comment. I will see if I can dig up some info on this for you cheer
Video looks compelling. Can anyone explain what is meant by low /high pressure systems?
Thanks for the comment. To be honest majority if not all pond systems in the uk are relatively low pressure. A bead filter prob the highest but that’s only 1.5bar max. High pressure usually industrial which is what pressure pipe is made for, gases or pumping liquids high up or for machine use. Some swimming pools especially for leisure may need high pressure pumps etc to pump water high up to water slides etc.
Hi. I am new to ponds and I want to build my own . Would you mind advising me on what size drain and pump and filter to use for a 10x7x4 for koi. Many thanks Dan.
It’s under 2k gallons so a theee inch would be more than enough
I think this video helped settle my mind. I have a 2" bottom drain installed with 2" pipework. This will be connected to a nexus 220 via a 4" to 2" reducer. Does this sound ok?
How much water is in your pond and how fast is your pump? Cheers for comment
@@thep0ndman Pond is 12000 litres. Have a 20'000 lph variable pump.
@@MickysAquariums the 20k will be too much on full but good that you slow down. Use 3” if you want the full 20k also depends on bends etc to take friction into consideration
@@thep0ndman The 20k was all they had in stock. 10k would have been enough. Will be running it around 6-8k. Five 90 degree bends from pond to filter.
@@MickysAquariums what did you end up with 2" or 3" and did it work ? How was 20,000lph on the nexus 220 ?
I'm confused. If chamber 1 and 2 are the same level, no water will flow from one to the other. Isn't it the drawdown that gives you the flow?
It’s just to show that the flow rate of your pump should determine the size pipe you need. Cheers thanks for the comment
Pondman, if I switch from 75mm pipe to 63 or 50 at the bd purge valve, then run the last few inches into filter at that size, does that reduce the diameter flow of the full length? 75mm ball valves are expensive so was going to reduce if it didn't defeat the object of having 75mm from bd.
hi Adam, what pipe are you using firstly? Pressure / waste? to be fair it will slow the purge down but tricky to say how much or any enough to effect it as it is at the end on a short piece of pipe...
@thep0ndman I'm using pressure, but only because I got a good price, I know what you've said about overkill 😊....I'm just unsure as to whether swapping out to 63 or 50 directly before the filter would in fact reduce the entire run to the same diameter given thats the diameter it will need to exit through into the filteror whether it wouldn't affect the flow rate. Thanks for your time and effort
So your saying two 2" bottom drains will handle 25000l why make it go to a 4" pipe then?
That’s the point of the video. Majority of ponds will never need 4” pipe work, 3” prob best for most, 2” for the smaller ones but it can depend on how far you plan to install the filters and how many bends as there is friction (small amount) on the 2” versions
Hi mate I was going to have a 4"bottom drain but after watching this vid I'm thinking that's the wrong size for my pond if you could give me some help it would be much appreciated my pond is going to be 10x7x4ft which on pond calculator says it's 7,925.73 litre. going to run a 10000lph pump three barrel system with k1 in if I'm reading this right could I put 2-inch drain?
Thanks for comment. If you go for a 2” just bare in mind the distance your filter is away from the pond and also how many bends you will have just to allow for friction. If I was you if you can inc pump to 14k and use a 3” to keep things simple. Perhaps have more than one inlet from the pump so you can get a nice direct flow, maybe aim one inlet diagonally towards the base to help avoid settlement. Also not sure if you’ve seen this video as most people think you have to have a gravity filter system with a bottom drain, you can go pump fed th-cam.com/video/OsXPtW_Tae4/w-d-xo.html
Ok thanks will take your advice and go for the 3" and go for a bigger pump. I have seen video you Linked already👍. interesting but doing it that way is before the filter. so the muck goes to the pump first and then gets mashup through the pump. before going to the filters which would make it finer. I was thinking that the muck would be better going straight to the filter as it's not broken down first. On a similar note about pumps don't know if this is possible. if you put a wet pump in a bowl/tub of water after the filter system plumbed in as you would a dry pump. but submerged in water in the tub could that not be used to run the system. because the tub of water should keep the pump from over heating. which is why you can't use a wet pump as a dry pump?
Thanks for comment. I see your point about the pump before but I assure it makes no difference as it goes through the pump so quickly, not like a food processor. After the filter is good aswell what ever you prefer. There are many types of wet pumps that can be run dry. These are a good budget pump by oase that can be installed dry or wet, they do a 14500 www.sussexpondsupplies.co.uk/collections/waterfal-filter-pumps/products/aquamax-eco-classic-solid-handling-waterfall-filter-pump-extra-large-ponds?variant=19075268214857
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