Pool / Spa Return Design Questions

[bobjtx]

Hi, I am getting ready to start our pool build, and had a couple of questions on how many pool returns to use, and how this works with the Spa. Hoping somebody can help out, as we excavate on Monday. Have searched for this, but did not see anything that related to placement based on this type of pool shape. Some background: 20k pool, 525 Sqft, 110' perimeter, 6'x6' Spa, Pentair VS pump, 520 sqft filter, 400k heater. Running a pool & Spa off single Vs. pump (Pool/Spa combo).
Plumbing: 2" looped pool return line, 2" dedicated pool drain line, 2 skimmers each on dedicated 2" line (3 x 2" suction lines total), 3" Spa drain line. 2.5" Spa jet looped line, 2" Air return (to spa), 5 Spa jets total. 6 Deck jets, 1 bubbler in the tanning ledge. Pool is ~23' from equipment pad, Spa is ~40' from equipment pad. With two turnovers / day, the estimated pool return flow is 27 GPM (20000 / 24 / 60). With 7 returns, that's ~4 GPM per return.

QUESTIONS:
1. Do I need to run a separate pool return line to the Spa for filtering when in Pool mode, or do I just use the Spa jets for filtering by not closing the Pool/Spa return Jandy valve completely (i.e., pegged for 90% closed position)? Since filtered (& heated) water goes to the Spa jets and to the pool returns, depending on the position of the 3-way Jandy valve that switches between pool & spa mode, I wasn't sure if the Spa needed a separate pool return. Is there an advantage in doing it one way Vs. the other?

2. Given the pool shape in the attached JPG below, how many returns should I have and where should they be placed? It seems the rule of thumb is 2 at least 2 returns per skimmer, and the intent of return placement is to circulate the water past the skimmers to both mix/circulate sanitized water, and to skim off debris before it falls to the floor. That said, with an irregular pool shape and a tanning ledge are more returns needed? My plumber suggested 6 in the pool based on the pool shape + 1 in the Spa, but said the final placement is up to me. 7 returns sounds like a lot (lower GPM per return), but maybe not? Would appreciate some design input from plumbers or pool builders.
Thanks!

Pool Diagram:

 

[JasonLion]

A separate return in the spa is very nice, but not essential. That allows you to pre-heat the spa without running the jets and allows for future flexibility if you ever want to have a separate spa pump.

There is nothing wrong with having 7 returns, aside from some very minimal additional cost. In fact it can be very handy for an irregularly shaped pool. Looking at your diagram, I would get rid of the return closest to the "6 x Deck Jets" label, since the one below it should take care of moving the same water that one would, but that is not really a significant issue. There are several different "schools" of plumbing design, the most popular approach these days is to have lots of returns. There are other approaches that also work well, and can use significantly fewer returns, but it is essentially a "style" decisions rather than an important functional point. Having extra returns usually makes the plumbing more efficient, though the effect is small. On the other hand having lots of returns means more things that can break and need to be dealt with when winterizing, but again the difference is fairly small as returns don't tend to break.

 

[bobjtx]

Thanks for the quick response Jason. That "different schools of thought" explains the discrepancies I have seen when researching this, and makes sense. Very much appreciated!

Bobjtx.

 

[bobjtx]

One more question. The plumber did NOT create a loop for the 7 returns. :grrrr: I am arguing with him now to get this fixed, but I have gunite scheduled for tomorrow morning before rains come in, so it would be bad to have to wait. If I can not get this remedied in time for gunite, how "bad" is having the returns "T"'d (3 on one side, 4 on the other) vs having these connected in a single return loop? i.e., with 2" return pipe, how big a difference would I see on the first vs last return (last 4th return is in spa ledge). I plan to be running 1 -1.5 turnovers per day, so 20ish GPM for normal filtration which is ~ 20/7 = 3 GPM per return). I know a loop would be better (it was in my bid request, in my drawings, but the plumber seems to want to do things the way he has always done them - arghhh!), but I need to know how big a deal this is.

Thanks!

 

[Bama Rambler]

Blowing gunite shouldn't affect the ability to loop the return plumbing. Unless he stubbed them too close to the pool wall and will have to replace the stubs. Other than that, the only thing that would affect that would be if your pouring decking.

 

[mas985]

If I can not get this remedied in time for gunite, how "bad" is having the returns "T"'d (3 on one side, 4 on the other) vs having these connected in a single return loop?

Loops help but aren't perfect either. A teed configuration can be just as good if not better than a loop if done properly. The key is to have approximately the same number/type fittings and pipe length for each of the ports. Also, it helps to up size the pipe so the pressure loss is minimized and any differences are negligible. True of loops too.

 

[bobjtx]

Thanks to all for the quick responses.
Returns are being run in the back of the 12" bond beam due to two factors: Highly expansive clay soils in our area, so encasing plumbing in concrete where feasible (where it can be done without compromising the 9" wall/ 12" bond beam) minimizes pipe flexing leading to potential leaks. This is why I need to get this addressed before gunite is sprayed.

Mas985 - always glad to have your input. Flow through the returns is expected to be between ~20 - 40 GPM, based on 20,000 gallon pool and 1-3 turns per day. I am trying to build the pool to be as energy efficient as feasible, so will want to try to run lower turn rates. 2" piping should be able to carry ~84 GPM @ 8 fps, so the resistance is minimized. It does not look like any real thought was put into specifying the distance between returns, although fittings are identical. Mas985, based on your response, I'm thinking there may not be too big a difference?? The unknown, is the 7th return (4th return on one leg of the 1 "T"). I do have a bubbler in the tanning ledge that will help move water, so perhaps it won't be that big of a deal?.

One other item while I am at it. Despite my asking for a separate filter return in the spa, the plumber emphatically stated I did not need one there. Later he came back and highly. highly, recommended I put a 2nd bubbler in the Spa floor. Though I did not really want one there, I was not opposed to it and felt it could act as a return in the Spa. Perhaps I should just set up the Jandy valves so they only close like 90%, thus using them as a return in the ledge and a return in the spa? Is that acceptable?

Lest you think I am just letting him push me around, there are multiple other items I have had to get him to change because he would not follow the design document, so now I am at the point of trying to pick my battles.

Thanks for the assist on this.

 

[mas985]

Loops really only help when there is a large asymmetry in the plumbing layout (i.e. twice the returns on one side vs the other or significantly longer runs).

I would highly highly recommend separating the jet function from the circulation/filtering/heater (i.e. separate spa return). Even if you have only one pump for both functions now, you may want it down the line and now is the cheapest time to do it. But one thing to definitely avoid is running high flow rates through the filter and heater which is why I recommend having two pumps and separate loops for the spa jets and return. It can be done with bypasses but I like having the ability to run the spa jets separately while filtering the pool.

I am trying to build the pool to be as energy efficient as feasible, so will want to try to run lower turn rates. 2" piping should be able to carry ~84 GPM @ 8 fps, so the resistance is minimized.

Then I would target closer to 6 ft/sec. The 8 ft/sec target is more or less a maximum velocity that the plumbing should not exceed. Regulations (VGBA) in many areas now dictate a maximum velocity for the suction side of 6 ft/sec. Having larger pipe never hurts and usually doesn't cost much more, plus it makes the imbalance in the returns less critical.

 

[bobjtx]

Thanks Mark. We should be closer to 4-5 fps, so it sounds like we are OK. Got the plumber to come back and finish the loop, but he did not want to pressure test as it was late and water would need to be drained in case of a freeze. I am going to try and do the pressure test myself today. I should just need to put the plugs back in the equipment, connect the water hose, fill with water and bleed off the air to pressurize the lines. His gauge and bib connections are still attached to the plumbing, so hopefully this will not be a big deal. My understanding is that the pipes should hold 25-30 PSI for at least 15 minutes. Anything else that I might be missing for this test? I think after this question I will start a new "under construction" thread to address multiple different questions going forward. Thanks for the assist on this - I really appreciate it.
Bobj.

 

[mas985]

I would test at 45 PSI but that's just me. 25-30 is a little low.

 

[bobjtx]

Understood. Thanks.