Staggering/Stacking Gunite Spa Jets?

[Sclib]

Hi all, I looked before posting and did not see a thread addressing this specific issue. We are in pre construction on a Gunite Spa. Understanding that there are a lot of variables that effect jet pressure, posting this for review and comment.
Building a 11x8’ Gunite Spa with 8 Waterway Jets. Hayward VS 950 2.7 max HP pump with Omni Logic and about 10-12‘ straight line from pump to waters edge. Builder is fighting me a little on stacking (1 above the other) or staggering (6” to 10” height from seat).....he is afraid of pressure loss at jets. He is advising a second loop for the lower jets on the system.
My question is does anyone have experience with stacking or staggering their jets on a single loop and if so what were/are the results? My idea to combat pressure loss (without adding a second pump) is to do first seat with two 9”high jets 6” apart (my mid back) then next 2 seats with single jet at 8” then next 2 seats with single jet at 7” then last seat with 2 jets stacked at 7” and 10“. Again, anyone with actual real life experience with this scenario? Right now we have not planned on a Blower but understand that could increase our pressure and is easily added now or down the road.

Thanks in advance for any insights.

 

[ajw22]

What size pipes will be used to the spa jets?

I think your PB is correct and trying to protect himself from complaints on inadequate pressure at the jets and a poor spa experience. It can maybe be done with the right hydraulic design but it sounds like your builder does not have the knowledge to do the calculations.

Let's see what @mas985 says.

 

[mas985]

First, blowers don't add pressure. They simply add air which is a lot less dense than water. Water velocity creates the pressure against the body. Blowers are typically used by PBs to help clear the air line of water. But if the spa is designed properly, a blower should not be needed.

As for putting the two levels of jets on separate loops, that shouldn't make a big difference, again if the spa is designed properly. Having the jets as different depths shouldn't really change anything because any static head differences net out to zero.

The important thing is to use large pipe, both air and water, (at least 3" for 8 jets) to/from the spa and to use large pipe (2.5") for the loops at the spa. This will minimize head loss between the jets ensuring they have the same pressure.

BTW, what orifice size jets are being used (i.e. gpm/jet requirement)?

 

[Sclib]

Thanks all for the quick replies. As far as pipe size, I know they are starting at 3” and I believe going down to 1 1/2” at the spa shell. I attached a screenshot of the plumbing breakdown but it is not super clear. It shows standard runs and then upgraded to 3”. Not sure if this helps you. The 1 1/2” is not shown on the screenshot, this was just told to me by the builder. As far as the orifice question....I do not know answer to that but will try and find out.

 

[mas985]

It looks like 3" is for the pool, not the spa. The spa appears to be using 2" pipe but it isn't clear if they are running multiple pipes. You probably should get some clarification on exactly how the spa is plumbed. Just a warning, PBs are notorious for screwing up spas. The forum is littered with unhappy POs because of this. I can't stress this point enough, get the details on EXACTLY how the PB is going to plumb the spa and make sure you sign off on the design and plumbing installation.

 

[Sclib]

It looks like 3" is for the pool, not the spa. The spa appears to be using 2" pipe but it isn't clear if they are running multiple pipes. You probably should get some clarification on exactly how the spa is plumbed. Just a warning, PBs are notorious for screwing up spas. The forum is littered with unhappy POs because of this. I can't stress this point enough, get the details on EXACTLY how the PB is going to plumb the spa and make sure you sign off on the design and plumbing installation.

Thank you for the wisdom. Actually there is no pool...just a large spa. And I know they are running just what they are calling a single loop for the jets. They are wanting and xtra $2000 if I want to put in a second loop (for lower jets) and a second pump ($1600 pump....not a second VS 950 and $400 for the plumbing). I will pin them down on the layout but since I am the one requesting the staggered/stacked design, they want me to sign an addendum that says that some jets may have less pressure and that I understand that. They have been building Pools and spas for 20 years so not fly by night but I fully understand what you are saying about maybe maybe not understanding pressure issues. Is there a way they can run the plumbing plan past Hayward and see what the Hayward techs think?

 

[jimmythegreek]

If your looking for strong therapy jet action a second loop and pump is the way to go.

 

[mas985]

I agree with JTG. Two loops is the way to go.

However, there are couple choices with the loops. Generally, I like the idea of the jets being on a separate loop from the filter and heater. Without the filter and heater, you will be able to get well over 15GPM/jet. That setup will even support 20GPM/jet.

 

[jimmythegreek]

Good point mas, would definitely add some extra power to the jets