Pool Plumbing Design Questions

[bobjtx]

Hi, first time soon-to-be-pool-owner and first post to the forum. That said, I have been scouring the forum for the last 2 years in anticipation of building a pool (thought about trying the owner/builder, but am holding off to see if I can get a decent build from a PB first). Currently, we are talking with PBs about a ~15'x30' play pool (3.5' - 5' deep), with Spa and 9x6 external tanning ledge (6-8" deep). Total gallonage ~16,000, Pool area (including spa and ledge) ~500 sft, Perimeter - 105'.

Pool: 2 skimmers, split drains (all with separate runs to the pad), 4 returns, 4 aerators (to cool the pool in the summer here in N. TX), 1 bubbler (~15-20 gpm) in tanning ledge, two scupper/urns (~6-15GPM/ea).
Spa: 5 jets (15-20 GPM/ea)
Pump: Pentair VS 3050
Filter: Either a Pentair 420 or 520 Clean & clear cartridge filter.
Heater: Pentair Mastertemp 400k BTU
Polaris 280 Pressure side cleaner with booster pump.
Equipment pad located 26' from one side (water edge) of the pool. Spa located a bit closer to pad.
Sanitation: BBB (future liquidator / peristatic pump)

I have two different quotes from two different PBs, but neither PB specifies much detail on the plumbing. I want to keep the head pressure low to allow for efficient running (less costs) but before I talk details with the builders, I want to make sure I understand the plumbing needs for an efficient pool. From reading threads here, and the "Have you lost your head..." thread, my understanding is that the following would be preferred:

- 3" PVC lines for the skimmers and drains, each a separate run to the pad.
- 2.0" PVC line to 4 looped returns with 1 ball valve (max 3 daily turns = ~33gpm, 1 daily turn = ~11 gpm)
- 2.0" PVC for looped 4 Pentair aerators with 1 ball valve (could not find GPM for Pentair aerators, but assuming 6-10 gpm/ea)
- 2.0" PVC for Bubbler ~10-20 gpm with 1 ball valve. (Could use 1.5", but might as well keep things the same)
- 2.0" PVC looped for 2 scuppers with 1 ball valve (6-20 gpm /ea).
- 2 x 2" or 1 x 2.5" PVC for looped spa jets (5*20 gpm/ea = 100 gpm)

Desired Operation Modes:
1. Filtration only (11 - 33 gpm)
2. Filtration + bubbler (~31 gpm)
3. Filtration + aerators (~40-51 gpm)
4. Filtration + bubbler + aerator (~71 gpm)
5. Filtration + bubbler + scuppers (~71 gpm)
6. Spa jets no heat, no water features (~100 gpm)
7. Spa jets with heat, no water features (~100 gpm)
8. Heat pool, no water features (~?? gpm?)

Questions:
1. Do the PVC sizes above appear appropriate?

2. I COULD use the Vs-3050 to run all modes, but do I need to add a separate pump for the spa? I ask, because of concerns I have read here about trying to push too much water through the filter (~100 GPM max). If so, what size is recommended - 1 HP or 1.5 HP?

3. Do I need a filter bypass when running multiple water features with filtration (~71 gpm)? I know that filters filter better at lower GPM, but at what GPM level is a bypass appropriate?

4. Aerators are above the waterline to spray water across the pool to cool it (much like the home made PVC aerators I have seen on this site). Does anyone know how well these pentair units work? Should I use 4 or go to 6 aerators (fairly cheap). I assume too many and the pressure will decrease at each aerator, making them less effective? (Do not know what the recommended GPM is for each pentair aerator).

5. Can aerators be run in PLACE OF the returns when you want to cool the pool, or should they be run at the same time as the normal returns. I would think they could be run in place of the returns, but am not real clear on the aerators' effect on chlorine levels (spraying in the air).

6. Do I need additional drains (suction intakes) to accommodate the water features, or is the existing drain sufficient (3" PVC should be capable of handling ~70 gpm mode easily, correct)?

7. How do you heat the pool? Do you heat the spa and let the heat migrate to the pool via the spill over, or do you heat the return water for both pool & spa (seems better)?

I would appreciate your thoughts on these design issues so I can get this straight in my head before discussing in detail with PBs. Might also help others trying to get a handle on this level of detail.

PS. I am not afraid of technical details, as I have a degree in mathematical modeling of fluid, thermal, mechanical, and electrical systems. Been a while since I had to use this, but I can most likely follow along with your technical reasonings.

Thanks for you time!
Bobjtx.

 

[JasonLion]

1) There isn't much point in using 3" PVC on the pool when you are already running more than one pipe in the same direction. 2" will be fine. On the pool you have basically oversized every line except the returns. Meanwhile, 3" is a good idea on the spa, especially if your 100 GPM number is correct. Of course, not very many jets are actually 20 GPM.

2) A single variable speed pump will be fine. If you have a concern about the filter you can install a filter bypass.

3) Really only when you are in spa mode.

4) It is really a visual thing more than a function thing. 4 jets is plenty for cooling in all but the very hottest climates. But six can look nice is some situations.

5) You don't want to turn the returns off completely. I also think the jets will use lower GPM than you listed.

6) You are fine.

7) Everything going through the filter should also go through the heater. You can heat the pool or the spa or both.

 

[mas985]

1. I would use 3" for the both suction and return of the spa. 3" may be a little overkill for pool since I am assuming you won't be running that at 100 GPM.

2. It is usually a good idea to run the jets on a separate spa pump to limit head loss and flow rates through the other equipment. You can still have a circulation loop for the spa where the main pump will filter and heat the water. Even if you went with one pump, it would be a good idea to have separate loops for the circulation and jets so when the jets are running, you can bypass the equipment easier.

3. See #2.

4. Not much of a comment but keep in mind that cooling a pool that way will evaporate a lot of water which means if you have hard fill water, there will be an accelerated build up of minerals in the water.

5. No comment

6. Remember that you are splitting flow rate between three lines so really 2" is probably sufficient but 2.5" would allow for isolation if needed.

7. Neither. I would go with solar.