Pipe size

cncelctrc

Bronze Supporter
Aug 28, 2017
24
Wichita KS
I need some advice on pipe sizing. I have read some posts on here about pipe sizing and head, but still can't quite understand it. My pool will be 29250 gallons. I have a Hayward EcoStar variable speed pump with 2 skimmers, 6 returns, and no main drains.

My pump will be located about 120 feet away from the furthest skimmer. I was planning on running separate 3" suction pipes from each skimmer back to the pump and then separate 2" pipe for all 6 returns. I will have Jandy valves on all lines to control flow.

Are my pipe sizes ok? Most threads say to go with bigger suction pipe but others say it is overkill. The distance from the pump to the skimmers concerns me and I think bigger pipe will help.

After reading Hydraulics 101 thread, there was a table called Equivalent Pipe/Fitting Size. Then it stated "On the return side of the pump, multiple lines can help reduce head loss as well but the number of return lines should never exceed the number of suction or pump cavitation could become an issue."

Since I have (6) 2" return lines, that equals 4.81" according to the table. There isn't any values for 3" pipe, so I can't find what (2) 3" suction pipes are equivalent to and then compare it to the return.
 

CJadamec

TFP Expert
Apr 29, 2016
2,390
Quaker Hill, CT
If you are running individual return lines to each return fitting 1.5 inch for each return is plenty of flow. You will want to run them all back to a 3inch header and have a valve on each line so you can shut off a return and or balance the flow between all the returns. if you are running individual pipes to each skimmer 2 inch is plenty. Again you can run them to a 3 inch header going into the pump if you wish. Valves again to shutoff and balance flow.

Unless your runs to the equipment are super long 3 inch isn't going to gain you much especially if you are doing individual pipes to each skimmer/return. There is significant cost increase when going from 2inch o 3inch schd 40 pipe and fittings. In 3 inch pipe you will need a plumbing supply house for schd 40 fittings home Depot and Lowe's only carry DWV fittings for 3 and 4 inch PVC.
 

mas985

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May 3, 2007
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After reading Hydraulics 101 thread, there was a table called Equivalent Pipe/Fitting Size. Then it stated "On the return side of the pump, multiple lines can help reduce head loss as well but the number of return lines should never exceed the number of suction or pump cavitation could become an issue."
Here return lines means from pump to pool. If you have a single return line from the pump to the pool and then it spits into 6 returns, that is considered a single run. However, it would be a bad idea to have 6 separate returns lines from pump to pool and 2 separate suctions line pump to pool all the same size. This creates a head loss imbalance between suction and return side. You will have less issues with the pump if the suction head loss is much less than the return head loss.

Since you have two suction ports, I would go with two separate suction lines pool to pump with a valve on each of them and on the return side, go with a single return line that splits into 6 lines at the pool. All of the pipe can be 2" to simplify things.

A slightly lower head loss design would be to use 2x2.5" suction lines and 2x2" return lines split 3 ways each at the pool. The larger suction pipe would allow you to run off of just one skimmer without any difficulty should you ever need to. Running of a single 120' suction line would likely create air leaks at the pump unless you only run on lower speeds which is also an option. But I don't think you need 3" lines. 2 1/2" is more than sufficient.

Really most of this only matters when running at higher speeds/flow rates. Running at lower speeds can compensate for almost any type of imbalance.
 

cncelctrc

Bronze Supporter
Aug 28, 2017
24
Wichita KS
Thanks Mark and Chuck for taking the time to give me some good info and suggestions. With my vari-speed pump, I was planning on running at lower speeds. I would really like to have each return controlled by a valve back at the pad rather than single or 2 return lines splitting at the pool. I don't care about the added cost of a lot more pipe. I am an electrical contractor by trade and my supply house sells both electrical and plumbing, so I get much better pricing than at Lowes or Home Depot, plus I can get all the correct fittings. I really want the benefit of being able to control each return separately and in the event of a leak can shut off that line. I had originally considered pairing up returns and then having just 3 return lines going back to the pad. But after reading many suggestions on this site of the benefit of controlling each return separately, I really liked having more control.

I totally understand that having 2 suction and 6 returns all the same size is a bad idea. That is why I thought 2x3" for suction and then 6x2" for return or even 6x1.5". Since I have long runs to each skimmer (120 feet and 95 feet), thought going larger to 3" would help after reading other threads on here about upsizing pipe on long runs. The return line lengths are about 125, 110, 100, 75, 70, and 50 feet. After getting more details of my setup and desire to control each return separately, what would you suggest then for pipe sizes on suction and return?

Thanks for all your help on this!
 

mas985

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That is why I thought 2x3" for suction and then 6x2" for return or even 6x1.5".
6 pipes from pool to pump is really excessive and total unnecessary. Why do you think you need to control each return? I have four returns and can honestly say that I have never had a desire or need to control flow to any of them. Controlling flow really means reducing the flow to some of them which I think is always a bad idea. Keep flow at 100% to all and you are almost always better off.
 

grottoguy

LifeTime Supporter
Aug 24, 2014
462
NJ
6 pipes from pool to pump is really excessive and total unnecessary. Why do you think you need to control each return? I have four returns and can honestly say that I have never had a desire or need to control flow to any of them. Controlling flow really means reducing the flow to some of them which I think is always a bad idea. Keep flow at 100% to all and you are almost always better off.
Maybe he wants to be able to turn a return off if there is a leak without affecting the other returns. If one pipe goes to three returns and that pipe leaks, he probably has to dig up the leaking pipe and fix it right away, but if each return has its own pipe, he could just shut it down and fix it at a later date or just ignore it. I don’t know anything about piping but am curious whether you think his idea is problematic due to plumbing concerns or head loss (or if you think it’s just overkill).
 

cncelctrc

Bronze Supporter
Aug 28, 2017
24
Wichita KS
I really like the ability of being able to control every return. Whether I need to or not, I would be nice to have that option. Just seems to make more sense and after reading the subject on this site, most have said the same thing.

I do trust whatever you say Mark. I have only been on this site for about a few months researching how to build this pool, and from your Hydraulics 101 and Plumbing loop analysis articles, you know what you are talking about. I'm just a little confused because from what I read on most of your posts and replies, was that you seemed to favor multiple return lines. You even showed in your plumbing loop analysis that 4 returns all with separate lines had the lowest head loss of any of the configurations and you said it gave the most flexibility and best performance. Just threw me for a loop when you recommended earlier to me for my 6 returns that I should run a single line split into 6 or 2 lines split into 3.

I really don't like the idea of one return line split 6 ways. That is what most of the pool contractors do because it is the easiest and cheapest. Seems like the vast majority on this forum recommends multiple returns from pad to pool. Because I am new to a pool, I have to base all my decisions from recommendations from those that have the experience. Since you don't recommend 6 separate return lines, how about 3 lines with 2 returns on each? That would still give me good control over 3 pairs of returns. If in worst case scenario have a leak in a return pipe, I can still isolate and not shut down everything and still have good circulation with 2 lines and 2 returns. If you think that will be good, what size of pipe for the 3 return lines, plus what size pipe for the 2 suction lines? Based on what you recommended in your Maximum flow rates for PVC pipes post for 2HP pumps or greater, would be two 2.5" suction lines and three 1.5" return lines. You posted that over 10 years ago, so just checking if you still recommend that.

Thanks for all your help. I have the hole dug and all the steel wall panels in place. Getting close to pouring concrete collar and then I will be doing the plumbing in a week or so.
 

mas985

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I was mostly interested in your motivation and expectations. I have read posts where the OP wanted to equalize the flow to all the returns and I just wanted to make sure that was not the goal because IMHO, that is totally unnecessary and actually worse than just leaving all the returns 100% open at differing flow rates.

There is no real downside to having multiple returns as long as it is balanced with the suction side. 2 Suction lines of 2.5" diameter are equivalent to a single line of 3.4" diameter. If you want 6 separate lines, I would not go larger than 1 1/2" or you will probably end up having to partially close off the lines to avoid cavitation which then obviates the need for a larger line. If you wanted to go with 3 lines, 2 returns each, you could go with 2". It is really a matter of your preference not mine.

But if you are really interested in having the most efficient system possible, then go with a cartridge filter or a DE filter without a backwash valve. Backwash valves have a lot of head loss and will make your choice of plumbing somewhat moot.
 

cncelctrc

Bronze Supporter
Aug 28, 2017
24
Wichita KS
Thank you for all your time and help. I will go with the 3x2" return lines. Since my skimmers are 120 feet and 95 feet away (approximate pipe length), is 2x2.5" sufficient for that long of a run or do I need to go 2x3"? Each skimmer line will have (5) 90 degree bends by the time it reaches the Jandy 3-way valve at the pump. I will try to use (2) 45s with 1-2 feet of pipe between to make all the bends. I may even try heat bending the pipe with long sweeps for all the underground bends. I do a lot of heat bending on electrical PVC conduit but never done it over 1" pipe, so will have to play around with it first. Will using the 45s or long sweeps help that much or is it that not much of a gain to worry about?
 

mas985

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2x2.5" should be more than sufficient.


I will try to use (2) 45s with 1-2 feet of pipe between to make all the bends.
2x45s have about the same head loss as a single 90 so not much benefit there.
 

cncelctrc

Bronze Supporter
Aug 28, 2017
24
Wichita KS
Hopefully this is last question. Started the plumbing on the pool and need to know the best way to connect the pairs of returns. The easiest is to run the pipe to the first return, tee it there and go to the next return. The other way is to run the return line to a tee directly between the 2 returns, and then equal runs to each return. Will this make much of a difference?
 

CJadamec

TFP Expert
Apr 29, 2016
2,390
Quaker Hill, CT
In practical terms there is very little difference between the two set ups. Either approach is fine use the one that allows you to have fewer fittings and easier plumbing layout.
 

cncelctrc

Bronze Supporter
Aug 28, 2017
24
Wichita KS
I got the plumbing for the returns ran, but came across a few posts on here that said your return runs should all be the same length. My 3 runs (2 returns on each) are not the same length, not even close. To the farthest return on each run are 125', 94', and 68'. All the return lines are 2" pipe. Is this going to be a problem? I still have all the pipe exposed, so if I need to make changes, now is the time to do it. I do have Jandy 2 way valves on each line on the manifold at the pad that I could use to help balance flow better.

Pool Returns.jpg
 

mas985

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I wouldnt get too concerned about the different lenghts. The flow rates will be proportional to the square root of the pipe length. The overall circulation will be better just leaving all lines open than restricting the shorter lines.