Pump Size

[stualden]

Thanks Dave. I'll always use a separate pump for the spa jets, so the existing 2 horse (or a direct replacement) should be okay for the spa. I read something relating hp requirements to number of jets - in this case I have 6 (it's a nice roomy spa).

I will get out the pencil and paper and the Ultra Flow charts and figure out what my requirements are for the main filter circuit. I suspect that 1 hp single speed is right (i.e., Sylvan sized it correctly). What I want to figure out is if the Ultra Flow pump can work with the lower RPM of a two-speed motor, and if so, what size motor will give best results for regular filtration at the lower speed.

[msm859]

Although the number of jets you have in your spa is relevant, it is probably more important what size pipe they used. My guess is a 2hp pump is TOO BIG. There are tables that will tell you how much flow you can run through different sized pipe.

[waterbear]

Spa jets require a more powerful pump in a shared pool/spa system. This also requires an oversized filter to match the pump. This is how my 6600 gal pool ended up with a 150 sq. ft. cartridge filter and 1.5 uprated whishperflo pump...defininately overkill for the pool but needed to run the spa! I am actually very happy with it...my pool stays crystal clear and I could probably run the filter for a year before the pressure rises enought to warrent cleaning (although I do clean the cart montly). I looked into a 2 speed pump but there was some concern as to whether I would actually have to go with a larger pump HP to be able to achieve adequite circulation on low speed with my setup when it was being designed.

[stualden]

Thanks everyone. I will check on sizing for the spa pump too.

In my case, the spa pump is on a separate circuit that is completely independent of the filtration circuit. In other words, the spa has two drain holes for filtration (which I normally don't use - only for draining the spa), two returns for filtration (which I do use, causing a waterfall into the pool), two drain holes for the spa circuit, and six spa jet returns. There is also an air blower in the spa circuit.

So in my case, I guess the spa pump sizing is primarily a function of how hard I want the jets to feel? The spa circuit is all 1.5" pipe.

If my pump curves (UltraFlow pre-94) don't show results for the low speed of a two-speed pump, does that imply that it won't work (or at least not well), or just that two-speed motors weren't common back then (1991)?