Plumbing pool are 90 degree angles allowed?

mikespoolfl

LifeTime Supporter
Mar 4, 2011
179
Florida
The only sch 40 sweeps 90’s that I’ve found are the ones for waste. They have a smaller glue area and a max operating pressure of about 25 psi (temps about 70 degrees F. would lower the operating pressure). So I would think they should only be used on the suction side.
 

taekwondodo

LifeTime Supporter
Apr 26, 2009
419
Your builder should be able to get them from his wholesale distributor... or, you can check local landscaping supply companies - Ewing Irrigation has the most awesome PVC connector section...
 

JamesW

TFP Expert
Mar 2, 2011
28,291
It depends on the pipe length, flow rate and water velocity. You don't want to put the full flow capacity of the IntelliFlo through 2-inch PVC.

I recommend a maximum of 63 GPM through a 2-inch PVC suction with any 90s, and 73GPM if the suction pipe will not have 90s.

I recommend a maximum of 73 GPM through a 2-inch PVC return with any 90s, and 83GPM if the return pipe will not have 90s.

You can use 2 45s instead of a 90 to avoid using 90s.

What flow rate do you expect to use?
What is the distance of the pump and filter from the pool?
 

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mas985

TFP Expert
LifeTime Supporter
May 3, 2007
14,800
Pleasanton, CA
Pool Size
20000
Surface
Plaster
Chlorine
Salt Water Generator
It kind of depends who's data you use. Some show 2 45's being the same as a 90 and some (Bell & Crane) show them being worse. If plumbed back to back, it would most likely be worse than a 90 due to the extra turbulence. Now if you can replace each 90 with a 45, then you can save on head loss but that requires creative plumbing.
 

JamesW

TFP Expert
Mar 2, 2011
28,291
This reference shows that one 90 is equivalent to 5.7 feet of straight pipe and that one 45 is equivalent to 2.6 feet of straight pipe. That seems to indicate that two 45s would be equivalent to 5.2 feet of straight pipe, so slightly better.

I think that the first key is not to exceed the velocity guidelines of about 6 to 7 feet per second for the suction and about 7 to 8 feet per second for the returns.

I think that the second key is not to create excessive head loss. When determining head loss goals, it can be useful to understand terms like "Return on Investment", "The Law of Diminishing Returns" and "Net Present Value".

For example, if it cost 100 dollars to increase the pipe size from 2-inch to 2.5-inch and the lower head loss would save 10 dollars per month in electricity to run the pump, then you would probably conclude that the return on the investment was worthwhile. This would means that the net present value of all future savings was greater than the increased cost (investment) today. This would be on the good side of the law of diminishing returns.

Example 2, if it cost 1,000 dollars to increase the pipe size from 2.5 inch to 3.0 inch and the lower head loss would only save you 1 more dollar per month, then you would probably conclude that the return on the investment was not worthwhile. This would be on the bad side of the law of diminishing returns.

To determine head loss goals, you should know factors such as the average and highest desired flow rate, pipe length, pipe costs including materials and labor for installing different size piping, pump cost as a function of head loss etc.
 

DigitallyChallenged

Well-known member
Oct 24, 2010
174
Eastern TN
JamesW said:
It depends on the pipe length, flow rate and water velocity. You don't want to put the full flow capacity of the IntelliFlo through 2-inch PVC.

I recommend a maximum of 63 GPM through a 2-inch PVC suction with any 90s, and 73GPM if the suction pipe will not have 90s.

I recommend a maximum of 73 GPM through a 2-inch PVC return with any 90s, and 83GPM if the return pipe will not have 90s.

You can use 2 45s instead of a 90 to avoid using 90s.

What flow rate do you expect to use?
What is the distance of the pump and filter from the pool?

Pipe length will be pretty minimal, guessing around 20 feet or less. Builder had mentioned using gentle nineties so I'm thinking that these are the sweep 90's.

Not sure about flow. I had read a post that salt generator wants 50gpm but to turn over pool I can run much lower. I'll never need full flow for 5400 gallon pool.
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
14,800
Pleasanton, CA
Pool Size
20000
Surface
Plaster
Chlorine
Salt Water Generator
All of these sources show two 45s as having more head loss than a 90:

http://plasticpipe.org/pdf/tr-14_waterf ... istics.pdf
http://www.pdhengineer.com/courses/o/O-5002.pdf
http://westerndynamics.com/Download/fri ... ttings.pdf
http://www.edstech.com/design-tools.html
http://www.pumpfundamentals.com/downloa ... apter3.pdf
http://www.uni-bell.org/resources/Chapter%209.pdf

So again, it depends on which source you use but from all of the sources I have seen, most have two 45s being worse than a 90. I had used Engineering Toolbox for numbers until I discovered that most engineering firms use numbers that are supported by the Crane studies. In fact, the equivalent length method has lost some favor amongst the experts as shown in this thread:

http://www.eng-tips.com/viewthread.cfm?qid=173164
 

waste

TFP Expert
LifeTime Supporter
Mar 29, 2007
4,161
Coastalish 'down easter'
ocular said:
Paramount recommend 2 x45 instead of a 90 when plumbing their PCC2000 main drain to the debris canister to prevent cavitation on the suction side.

Welcome to TFP!!

Thank you for posting this :goodjob:

I can easily see that 2 45*s are less likely to become congested by 'stuff' (that somehow bypasses the grate) than a 90*, which would lead to cavitation.

Mayhaps this issue should be considered when plumbing suction lines and have the head accounted for, when planning the size of the pump and filter.
 

ocular

Member
Nov 13, 2010
8
Good comment, Thats probably why they recommend two 45s rather than one 90 to allow debris, leaves and stuff thru to the basket canister rather than a significant increase in resistance per se.
 
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