TDH worksheet: how to read returns and suction lines size?

[pool_aholic]

Hi TFP! After years of planning, I'm finally ready to begin my DIY pool project, thanks in large part to this forum. I received the engineering drawing this morning, and to my surprise, I'm seeing larger pipe sizes than I expected for a pool that's barely 15,000 gallons. I'm attaching TDH worksheet here for advice. I was planning on running individual 2" lines for each of my suction components (two skimmers, main drains, and vacuum), as well as 2" pipe for each individual waterfall, bubblers, and a closed loop for all five returns. My question is, if I do it this way will I meet that "trunk and branches" spec, or am I forced to do what the worksheet says assuming I understood it correctly? If that's the case, what should be connected to those 3" and 2 1/2" pipes? Also should the pipes run all the way to the pump? Any advice is greatly appreciated, thank you in advance!

 

[PoolStored]

@mas985

 

[mas985]

Hi TFP! After years of planning, I'm finally ready to begin my DIY pool project, thanks in large part to this forum. I received the engineering drawing this morning, and to my surprise, I'm seeing larger pipe sizes than I expected for a pool that's barely 15,000 gallons. I'm attaching TDH worksheet here for advice. I was planning on running individual 2" lines for each of my suction components (two skimmers, main drains, and vacuum), as well as 2" pipe for each individual waterfall, bubblers, and a closed loop for all five returns. My question is, if I do it this way will I meet that "trunk and branches" spec, or am I forced to do what the worksheet says assuming I understood it correctly? If that's the case, what should be connected to those 3" and 2 1/2" pipes? Also should the pipes run all the way to the pump? Any advice is greatly appreciated, thank you in advance!

First, residential pools are usually not required meet a turnover requirement unless local code demands it and it looks like the engineer used turnovers to determine the required flow rate. Although it also looks like they used the wrong turnover time (2.52 hrs vs 6 hours). Given the number of water features you have, 101 GPM may not be to far off and the pipe should be sized to the maximum flow rate and that part is usually code. What are the flow rate requirements for each of your water features?

My question is, if I do it this way will I meet that "trunk and branches" spec, or am I forced to do what the worksheet says assuming I understood it correctly? If that's the case, what should be connected to those 3" and 2 1/2" pipes?

The branch is the pipe between the main drain pair which really should be 3". It is only about 3' and helps to minimize entrapment so I would keep that. Also, main drains are not really needed in a residential pool and if you want to prevent further issues with the MD leaking and/or clogging, which is not uncommon, you could just leave it out.

The trunk for the suction is specified at 2.5" and again, I would keep that because on the suction side of the pump, there are a couple reasons you do not to use smaller pipe. Suction pipe is prone to clogs and the larger the pipe, the better. Also, you should design the suction side plumbing so that you can isolate any single suction line and still be within 8'/sec. So I would keep this as well.

The 2" pipe for the return is actually a little small IF the maximum flow is actually 101 GPM in any part of the return plumbing. Florida has a maximum of 10'/sec on the return but that creates a lot of head loss and noise. I would limit it to 8'/sec. However, as the water features and returns get split up and as long as any one pipe does not exceed 8'/sec, 84 GPM, then it should be OK to use. You may just need to have a bit of 2.5" plumbing on the pad before the flow is split up.

Equipment Pad Best Practices - Further Reading

www.troublefreepool.com

https://www.floridabuilding.org/fbc/commission/FBC_1015/commission_Education_POC/646/646-0-MATERIAL.pdf

Every locality has different building codes so you may want to ask your local building department what is required for residential pools.

Also should the pipes run all the way to the pump? Any advice is greatly appreciated, thank you in advance!

Yes for each of the suction lines. Home runs are always a good idea in case one of them leaks or gets a clog, you can continue to run the pool.

 

[pool_aholic]

Thank you so much Mark @mas985 for all the details!!! Can't ask for a better explanation, will go as you are suggesting for sure, thanks again