90 degree elbows or 45s?

[sktn77a]

I'm looking at re-doing all of the plumbing on my pool between now and next spring. I have about a dozen 90 degree elbows (not street elbows) on my equipment pad and am considering replacing each one with two 45 degree elbows. Will this significnatly reduce my head pressure or should I just stick with the 90s?

 

[mas985]

Will this significnatly reduce my head pressure or should I just stick with the 90s?

No. 2x45s have about the same head loss as a single 90.

 

[sktn77a]

OK, thanks. I saw several posts on the internet some saying its better, some saying not.

 

[JamesW]

Going to 2" instead of 1.5" would help.

 

[mas985]

One other thing I forgot to mention is that with a single speed pump, lowering head loss increases flow rate but it also increases energy use so it may not give you the results you are looking for.

 

[sktn77a]

Going to 2" instead of 1.5" would help.

Would going to 2" pipe for all of the equipment with 1.5" pipe for suction (1) and return (3) lines be worthwhile or is the single 1.5" suction pipe limiting everything?

 

[mas985]

One other thing I forgot to mention is that with a single speed pump, lowering head loss increases flow rate but it also increases energy use so it may not give you the results you are looking for.

Maybe you missed this.

 

[sktn77a]

Yes, I saw that but wasn't sure how to interpret it, hence the question. So going with 2" pipe would make things worse?

 

[mas985]

It depends on what you define as better or worse. Exactly what are you trying to achieve?

 

[sktn77a]

Just trying to improve flow/decrease head pressure. I'm stuck with 1.5" plumbing below ground and have lots of 90s. Almost everything I've read says 2" pipe is preferred over 1.5".

 

[mas985]

Just trying to improve flow/decrease head pressure. I'm stuck with 1.5" plumbing below ground and have lots of 90s. Almost everything I've read says 2" pipe is preferred over 1.5".

For increased flow, yes increasing to 2" pipe will help improve flow rates. But again, it will also increase energy use. It is a trade off. Many people believe that reducing head loss will automatically reduce the power bill but it won't. The power bill will only be reduced by reducing RPM (two speed or VS pump) or by reducing run time. However, with larger pipe, you do get more flow rate so at the lower speeds, the pump can do more. But with a single speed pump, there is not really much benefit to increasing pipe size.

If your real goal is to reduce the power bill, you need to either reduce run time OR get yourself a two speed or VS pump.

 

[sktn77a]

Well, a VS pump is on the books also (Pentair/Sta-Rite MaxFlo VS 1.5hp), as is a new multiport valve (same Hayward SP0714T).

 

[PoolGate]

This question is asked a lot on a lot of forums. The short answer is "yes", 2 45's flow more than 1 90. The longer answer is more scientific but the farther apart the 2 45s are, the better the flow will be. Putting them back to back will still get you more than a 90 but not terribly significant. A "sweep" 90 usually is better than both if you can fit that into your plumbing plan.

 

[mas985]

According to the Crane TP-410 Technical paper AND the following document from the PPI (Plastic Pipe Institute, pg 174), 2x45s have about 5% more head loss than a standard 90. And those numbers are for isolated fittings, not back to back. So I don't think 2x45s are ever a good idea.

https://plasticpipe.org/pdf/chapter06.pdf

Another good source:

http://www.metropumps.com/ResourcesFrictionLossData.pdf

Here is the Crane Excerpt:

Help for calculating the friction loss for typical fittings

 

[PoolGate]

According to the Crane TP-410 Technical paper AND the following document from the PPI (Plastic Pipe Institute, pg 174), 2x45s have about 5% more head loss than a standard 90. And those numbers are for isolated fittings, not back to back. So I don't think 2x45s are ever a good idea.

https://plasticpipe.org/pdf/chapter06.pdf

Could be there is a LOT of Internet discussion on this very issue. But everything I found said 2 45s are better (from just a little to way better). Many are from hydraulics experts with documentation to back it up. I did not find anything stating the opposite. If I have a chance I'll take a look at what you posted to see the reasoning as it really makes no sense that it would be worse.

 

[mas985]

Crane TP-410 is the only real authoritative source IMHO. They are considered the hydraulics bible in the industry. But if you have other sources, then please post them.

 

[sktn77a]

Thanks guys. I guess this is a question that may need more data and controlled testing conditions for a definitive answer. My thinking is that I'll just use 90s where they make the most sense and 45s where they make sense.

 

[Dirk]

With no foundation in fact or expertise (but that's never stopped me before! ) , I second the one comment about sweep 90s. If you have room, seems like a sweep 90 should beat out a regular 90 or two 45s... You might see if you can find some hydraulic data on those...

I used them for my solar installation, which, when engaged, significantly increases the number of 90s in the water path (like by 10 or so!). And when they re-did my pad to integrate the solar, I asked them to swap out as many of the old 90s for sweeps that space would allow. I now only have a couple left (not counting what's underground).

I also added a flow meter which helps me determine variable pump speed for pool water turn-over rate, as well as figuring out the pump speed for providing the solar panels with what they require, without having to do all the math (if I could even figure that out that way). I'm also watching flow rate, along with filter pressure, to get an idea of system performance vs filter condition. The Pool Math app tracks that data for me, which I can then check up on periodically.

 

[mas985]

It is very hard to find swept 90s in Schedule 40. But what ever you do, do not use DWV fittings. They are not as strong.

 

[Dirk]

It is very hard to find swept 90s in Schedule 40. But what ever you do, do not use DWV fittings. They are not as strong.

OK, you just freaked me out. I ran out to check. Some of my fitting (90s and 45s alike) read "Schedule 40", some do not. None of my sweeps do. Can you tell by looking at them? One of my sweeps butts right up to a 45 that is definitely Schedule 40, and the thicknesses of each collar appear to be identical. Would the DWV fittings be noticeably thinner?