Considerations for Designing a Spa.

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minimonster17

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Jul 22, 2013
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What are some of the basic considerations of designing a well operating spa? I read the small section in Hydraulics: have you lost your head, but there wasn't much there beyond pipe sizing, 2.5'' vs 3'', and number of jets factoring into head calculations. I am aware of the severe importance of looping returns in spas.

However, I am unsure of how to decide how many jets to put in the spa. My parents' spillover spa only has 4 jets in a 6' circular spa, and it seems inadequate to me. My setup will be a 7-8' octagonal spillover spa into a 17x35 rectangular pool. The spa will have a dual main drain setup. The pump will be a hayward variable speed.

I am currently leaning towards 6-8 jets, but am unsure of figuring out if there is an optimal number of/distance between jets, or if it is mostly personal preference? Would 3/8'' be better than 7/16'' jets? What other factors do i need to take into consideration? I'm located near Tampa, FL, so no winterizing of the spa/pool will be necessary.

I have read on here that a lot of pool builders screw up spas, and I do not want to add to that statistic.
 
The biggest issue IS pipe sizing. Often times PB put in pipe that is too small for the required flow rate and the spa performance suffers.

But when determining the number of jets, flow rate becomes the biggest issue because you need to have a pump that will supply the flow rate. If you get too many jets, then you will need a second or even third pump. But 6-8 jets can usually be run off a single pump if they are 15 GPM jets.

The size of the spa comes into play too because 8 jets in a 7' spa makes for very close sitting. So you first need to decide on how many people do you want to sit in the spa at the same time and do you want a jet for each one. If you have teenagers, they love to cram as many in a spa as possible. 7' spa can easily support 6 jets while a 9' spa would be better for 8 jets evenly spaced. Then you have choices about floor jets and seat jets. The sky is the limit. You can look through the waterway catalog to get an idea of the different types of jets:

http://www.waterwayplastics.com/products/pool-products/gunite-jets/

Will you be having a separate pump for the jets or a single pump for both pool/spa circulation and the spa jets?
 
Unfortunately, in continuity w/ most other pool builders I read about on this forum, the guy I will be going with believes that 2'' pvc is adequate for the pool (pool will have 4 returns, btw), and 2.5'' pvc for the spa. The 2'' for the pool I believe to be ok, but would rather lean towards 3'' for the spa. The guy is probably the best/most respected in the area (Hernando County FL, two counties Northwest of Tampa) been in the pool building business since the seventies, w/o any complaints to the BBB or state registrar of contractors.

He plans for pool/spa to be run off one pump, the hayward ecostar variable speed. Water features will be limited to spa spilling over into pool, and spa jets. (Though I hadn't figured for, or knew of floor jets.) Would having a dedicated spa pump be a better setup, or will one pump for both the spa/pool perform equally as well? Spa will have an electric heat pump (house/neighborhood not setup for gas)
 
With 2.5" plumbing and having to go through the filter and heater (i.e. single pump), I would not go more than 6 x 15 GPM jets.

To get 8 jets, you would need two loops of 4 jets each and a bypass for the filter and heater.
 
Again, it depends on the number and type of jets you choose. First decide on the size of the spa, number of jets and type of jet. Then you design the plumbing around it.
 

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