Variable Speed pump "sizing" and how do I figure it out

[kelemvor]

Ooh I see some good reading in your signature links.. I know a fair bit about electricity, but when it comes to hydraulics... not so much.

I went outside to verify this stuff before I got back to you and found something that was a surprise to me. Most of the pool plumbing is 2" including the "spa drain" (suction side from the spa). The spa return, however is 1.5" at least near the jandy valve. The return jets appear to be 2" and there are four! There is a strange contraption (maybe a past repair? I bought the house with the pool) that reduces the pipe from 2" to 1.5" on the spa return. The spa is about 35 feet from the center of the spa to the pump assuming the underground plumbing is roughly straight with some 90 degree bends. So 40' for the furthest return, 30 feet from the closest. There is also an "air" pipe that is connected to the spa piping underground a further 10' from the spa. I guess this is where it gets the air to make the bubbles with, the kids blocked off one of the spa jets once and water came pouring out of that pipe...

Suction Pipe size: 2"
Return pipe size: 1.5"
Jets: 4 @2"ea
Distance from pump to spa: 35' approx

Hopefully that pipe reduction is some kind of design feature rather than a design flaw or (worse) a homeowner pipe repair. Not that it's relevant, but the "backwash" (really just a drain) and cleaner suction lines are also only 1.5" but without the strange coupler that is present on the spa pressure side pipe.

Photos:
exposed plumbing:
closeup of that spa return line:

[mas985]

I doubt you have 2" jets. Most spa jets are usually either 3/8" or 7/16". The jet nozzle is deep inside the pipe not near the surface.

But unfortunately, given you have such small pipe for the jets, that is most likely the cause of your weak jets. The EcoStar will help some but there is only so much you can do with that size of pipe. If you did have 7/16" jets, you might be able to replace them with 3/8" jets and the jet would feel a lot stronger.

But a bigger concern is with entrapment. With 2" pipe and such a big pump, you have the potential for some very serious entrapment issues. So if you do decide to go with a VS pump, please make sure you get the SVRS version of the pump.

[kelemvor]

The pool and the spa both have multiple drains in them, I assumed to reduce the entrapment risk. If that's not enough then I guess I'll have to put just a little more priority on this project I am considering.

I dug up the pipe under the "strange contraption" which it turns out is a spring check valve (that must not be closing correctly). Unfortunately, it looks like the underground section of pipe for the spa is also 1.5" .

Are the jets themselves something that can be accessed from the spa end of the pipe, or is that something that would require breaking up the decking to access?

[mas985]

Multiple drains do reduce the risk somewhat but because of the pipe size and pump size, the velocity can be quite high at the drain. Many cities now require both dual drains and SVRS especially for spas because the drains are not very deep.

The jets can be accessed from inside the spa end of the pipe. A socket wrench is used to unscrew them. Sometimes debris gets trapped behind the jets so it is a good idea to remove them and run the spa to flush out anything that may be there.

[mrrparker]

I am going through the same issue. It seems like the Variable Speed Pumps give you a one size fits all and then you tune it to meet your needs. The most popular is the Pentair Interlliflo but it only has a one year warranty. My issue with them is they have a lot of complaints and all they are doing is taking a 3 phase motor and mating it with a VFD. Minimally they should be giving 3 year warranty.

[BigDave]

My Hayward EcoStar SVRS has a sicker on it that says: 2.0HP, 1.35 SF, 2.7 THP if this helps at all - I realize this info is not on the Hayward website so I figured I'd share.

[kelemvor]

My Hayward EcoStar SVRS has a sicker on it that says: 2.0HP, 1.35 SF, 2.7 THP if this helps at all - I realize this info is not on the Hayward website so I figured I'd share.

Thanks very much. Sounds like the motor its-self is a little less powerful than what I've got, perhaps the impeller is better. I have no idea what my wet end is rated at, there's no markings on the pump that I can see other than the ones on the motor (which I replaced last year). I think maybe I'll try to find it local in the event it won't run the spa I could return it. My usual pool store wants $250 more than most sites online do, though.