Different pvc pipe sizes at construction site?

Tiburon

Silver Supporter
Dec 19, 2019
15
Sacramento, CA
Hi All,

The excavation was completed on Friday. This morning someone (plumbing crew I presume) dropped off a bunch of pvc pipes. I see a bunch of 2". But I also see a few 1.5" and 2.5" (see picture). The pool plans have it listed as 3" PVC for the suction (which I don't even have in the pool) and 2.5" for the pool returns.

Is there any reason to use 1.5"? Or 2" Or is it better to have all the plumbing the same size?

And if all the fittings for the pool equipment are 2" does it really help to have 2.5" anywhere?

Thanks
 

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TKR

Gold Supporter
May 21, 2019
51
Central NC
I am no expert but just starting plumbing my fiberglass pool. I maybe can shed some light, but not on specific pipe sizes which are driven by the details of your pool.

The plumbing design will combine different pipe sizes to handle pump capacity and the way you want to use your pool features. Bigger pipe handles more volume but is harder and more expensive to work with on small pool fittings. Smaller pipe may be too restrictive when combining multiple fittings. Multiple pipe runs and sizes are needed to control different items like returns, water features, skimmer vs drains etc.

There are two or more large pipes which the pump is using to pull unfiltered water out of your pool (drain or suction). These come from multiple drain fittings near the bottom and, from the skimmer at the top. Each of these is probably connected to a 2" pipe and (depending on your design) may then combine into a larger pipe (maybe 2.5") for the trip to the pump. If the pump is a long distance from the pool, the pipe run may then be sized larger to lower resistance (and load on pump).

The pump sends filtered water to back many locations in and around the pool and maybe in different combinations. So for example a simple return jet fitting will have 1.5" pipe connected to it. Multiple jets and may be combined into a 2" pipe. If a jet, group of jets, or water feature, is to be controlled individually, each needs its own pipe back to an on/off or selection valve in the equipment pad.

Ground water cannot be allowed to build pressure between the pool and the ground. They may be planning to use 3" pipe to drain water away from the ground around your pool (daylight drain or sump).
 
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Tiburon

Silver Supporter
Dec 19, 2019
15
Sacramento, CA
Thank you so much. That makes sense. It sounds like I will want to make sure that the upstream of the pump has the ability to bring in more flow with larger pipes, and below the pump it will be ok with the smaller pipes.

I have one skimmer and the split drain below stream of the pump, and 3 returns, a waterfall and water slide. So 2 coming in, and usually just 3 returns going out.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
12,833
Northern NJ
Tpically 2" pipe is used for suction lines from the skimmer to the pump and for equipment pad plimbing between pump, filter, and heater. Then 1.5" is used to the returns. Your builder can go larger if he wants but there is not much benefit.
 

JamesW

TFP Expert
Mar 2, 2011
17,330
You need to know the flow rate intended for each pipe. For suction, you want to keep the water velocity below 6 ft/sec. For returns, you want to keep the water velocity below 8 ft/sec.

Size.......6 ft/sec......8 ft/sec
2"..............63...............84
2.5............90.............119
3.0".........138.............184
 

Tiburon

Silver Supporter
Dec 19, 2019
15
Sacramento, CA
Right now they have 2.5" going from the skimmer to the pad.

They had a 2" going from the split drain into the skimmer. I asked them to run a separate line from the drain directly to the equipment pad from the drain so I can adjust each suction line individually. So now there is a second 2" going from the drain to the equipment pad.
 

JamesW

TFP Expert
Mar 2, 2011
17,330
I don't see anything in your signature that would require a really high flow rate.

So, the current plumbing should be fine.
 

Tiburon

Silver Supporter
Dec 19, 2019
15
Sacramento, CA
The plumbing ended up being fine. I got a separate line for each return.

The only issue with too small of pipes was that they used 1.25" electric conduit instead of 1.5" as I specified in the plans. It was a beast trying to pull 4 awg wires 200 feet. I almost gave up. But finally got it through.
 

wireform

Silver Supporter
In The Industry
Aug 15, 2017
848
Spring Valley, NY
The plumbing ended up being fine. I got a separate line for each return.

The only issue with too small of pipes was that they used 1.25" electric conduit instead of 1.5" as I specified in the plans. It was a beast trying to pull 4 awg wires 200 feet. I almost gave up. But finally got it through.
On electrical conduit there is code so beast or not you need to be sure that pipe is sized correctly. Just because you ended up being able to get it done doesn't make it code although I don't know the code.