New pool build -- pipes and pump sizes

[jasontx]

I am just starting the process of building a pool in Dallas. Most of the pool builders I've talked to here are sold on big pumps and small pipes -- which seems to be the opposite of what is recommended here. The pool design is for a 33'x17.5' 3'-5'-4' configuration with a 7' diameter spa, which I think works out to about 13k gallons. 2 skimmers and 5 returns, 6 jets in the spa. Am I in trouble with the skimmers being plumbed separately back to the pad but with 1.5" pipe? I'm not sure about the return plumbing. The spa is all 2". Currently spec'd is a 2.5 HP Jandy pump and a 1 HP pump for the water features (3 12" scuppers). They feel the 2.5 HP is necessary to run the 6 spa jets.

So does the separately plumbed skimmers make up for the 1.5" pipe or does everyone do that? It's just weird when the several PBs I talked to locally all seem to do things pretty much the same and it is different than is discussed here.

The PB is in the process of switching from Jandy to Pentair, so I might be able to switch to Pentair equipment with the Intelliflo 4x160 (for an upcharge of course). I'm kind of neutral on the Jandy vs. Pentair thing -- I think they both make good equipment. If I got the 4x160 I can expect some energy savings and their cartridge-y DE filter looks interesting (you can backwash or pull out the 4 cartridges and wash them off), but Jandy's PDA looks nicer.

I'm even more concerned with the plumbing and the Intelliflo 4x160 (that can pump 160 GPM and seems to like big pipes), especially since I would be one of my PB's first installations of it. Maybe they plan on automatically using bigger pipes when they go with it -- my salesguy wasn't sure. Hopefully we start the dig next week.

Sorry for the length of this. As I'm a newbie I've been reading all the great information here for awhile. I appreciate any advice you have to offer.
Jason

[eljefe281]

I suggest on insisting upon (at least) 2" pipe everywhere, unless smaller is required local to a particular item (for example, to connect to a 1.5" return).

One other thing to consider. Most builders want to use the main circulating pump to feed the spa jets. This has the effect of oversizing your circ pump. Since you will run the circ pump far more than the spa, this will increase your operation cost.

I added a separate pump dedicated to the spa jets. This will cost more, of course, so you'll have to see if your budget allows it.

I have a two speed, 1 HP main circ pump and a single speed, 1 HP spa jet pump (plus a waterfall pump).

The benefits of this arrangement include:

- Not having to use 2 HP worth of pump while the spa is heating up (you don't run the jet pump until the spa is warm enough for you to get in).

- Being able to operate the spa as a "hot tub" (no jet action other than the very little bit of agitation provided by the circ pump pumping through the non-jet returns). To me, this is really a nice benefit.

Let me know if you'd like me to send you my plumbing diagrams.

[ehorn]

Wow that is the first I've heard of a PB using 1.5" pipes. Every builder in Tucson here has wanted to use 2.5" pipes. I'm not an expert by any means in pipe sizing for different equpiment. Seems you are better off with pipes that can handle higher water flow. The difference in cost for pipe diameter is almost negligable.

Good luck with the pool!

[jasontx]

I don't understand the 1.5" either when looking at the posts here, but I talked to multiple builders and they all said the same thing. That is why I am questioning that maybe the fact that they were running separate lines makes up for it. It is hard to imagine they are building that many pools and don't know what they are doing -- these are companies that build 300-700 pools a year. I will push hard to upgrade to at least 2" everywhere.

I asked every pool builder I talked to about 2 speed pumps and they all glazed over. My thought on that was build it as they usually do and when I gain more knowledge, replace the pump if I understand it well enough and think the savings will outweigh the cost.

I've read about your pool build eljefe, your pool looks great. So can a 1 HP pump drive 8 spa jets? They wouldn't allow me more than 6 even with the 2.5.

Thanks for the answers.

Jason

[eljefe281]

I've read about your pool build eljefe, your pool looks great. So can a 1 HP pump drive 8 spa jets? They wouldn't allow me more than 6 even with the 2.5.

Thanks for the answers.

Jason

Thanks for the kind words.

I have a 1 HP pump feeding 8 spa jets and they are plenty strong for my taste. I also have a blower to juice them up when I want more action.

Each of my jets is designed for 13 gpm, so eight of them would require 104 gpm. Remember, if you have a separate jet pump, you won't have the pressure drop of the filter, SWCG, heater, and three-way valves in that circuit, so a given sized pump will deliver more flow.

I looked up the outlet pressure that the jets are designed to operate at, added some pressure drop for the piping and the jets themselves, converted the result to feet of head, and selected a pump by reviewing the pump curves.

In any event, I can't imagine needing more than 1.5 HP for a spa jet pump service (separate from the main circ pump).

[mas985]

Just thought I would add my 2 cents here. I also have 8 jets on a standalone 1 HP pump but I wish I had a bigger pump. My jets require about 15 GPM each which is a total of 120 GPM. With the head loss I have, even with 2 1/2" pipes, I get about 13 GPM per jet and it is not as strong as I would like. So double check the jet rating to make sure you will be getting enough pressure and flow to the jets for your liking. Some people like strong jets and some weaker.

A variable speed pump would give you some flexibility to choose your strength but they cost over twice a standard pump.

On pipe size, you can actually get away with 1.5" pipes as long as you have parallel runs from the pool to the pad and you use all 2" piping at the pad. So each skimmer, main drain and return has it's own pipe. You can equate the number of pipes with the following equation derived from hydraulics:

Equivalent Diameter = Pipe Diameter * N ^ (2/5) ; where N is the number of pipes

So 2 1.5" pipes is about equivalent to a 2" pipe and 3 is close to a 2.5" pipe.

I think it is a better design to have separate lines to each suction and return port and a ball valve for control reasons but I would still go with 2" lines for each instead of the 1.5" lines to reduce head loss even further.

Some builders like to use a single 2.5" suction line from the pool to pad and a single 2" return line from the pad back to the pool. This however, does not allow you to isolate the main drain into the pump for draining and it is more difficult to control the flow in each of the skimmers.

If your builder is suggesting a single 1.5" line for the suction and return lines (1 each), I might look for another builder since he really does not know what he is doing. But then again, most builders don't. That's why I contracted my own pool.