Do I really need 2-1/2" spa return??

[MouseMan54]

Hi. I am doing a home addition and will have to move my equipment pad. It's going to a new spot in the yard.

While uncovering the pipes to reroute, I realized the return line from the spa is a 2.5" line. All other plumbing is 2", including the spa return. My question is do I really need 2.5 inch or is 2 OK. I'm considering reducing the line at the point I cut in to re-route. The return is from two drains in the spa. One on the lower side wall and one on the floor. It is about an 8' circular spa, attached to the pool with a spill way.

The only potential down side I see is potentially lower flow when running in spa mode. Since there is already higher back pressure from the spa jets anyway it doesn't seem to me the smaller return will have much of an impact. I'll also be upgrading to a 3HP Circupool variable speed pump when I move the equipment.

One more note. If anyone is thinking "don't question what the pool builder did" I don't give that much weight. There are too many bad parts of the setup for me to have any faith in what they did.

Thanks as always.

 

[setsailsoon]

mm,

Line size is calculated based on desired flow rate and pressure drop. Most of the time the return line is larger because it is taking suction from the bottom of your SPA. Discharge pressure and back pressure doesn't really affect the fluid mechanics in the suction since it all dumps into the SPA at atmospheric pressure. So all you have as driving force is the height difference and the suction created by the pump. Not saying it won't work but you need to do the calcs to ensure you don't have too much pressure drop in the pump suction. Need more information to check the calcs and there are some top notch fluid mechanics experts that would help you on here. I have some of the work they've done linked in my signature.

I hope this helps.

Chris

 

[mas985]

There is no downside to large pipe but a lot of up side. The cost difference is insignificant.

How many jets are you running? For 6 jets, both the suction and returns should be at least 2.5". 8 jets and I would go with 3" pipe. More than 8 jets and you will need multiple loops. You don't want much head loss in the lines or your jets will be very weak. Especially if you do not have a separate jet pump.

Also, VGBA requires less than 6 ft/sec in the suction lines. (90 GPM max in 2.5" and 138 GPM max in 3")

 

[MouseMan54]

Thank you both for the reply. Clarification and couple of follow ups. First, I realize I said return twice. The SUCTION line for the spa is 2.5. The return for the spa is 2. It's a 6 jet spa. When we use the spa, the valves are switch to all spa, so it is essentially a dedicated pump at that point.

Where I'm exposing the pipes to do the reroute is not all the way back to the spa, so sizing the returns is not an option. (Maybe in a few years when I get a remodel.) Being that the return is 2 inch dose that change anything? i.e. Have I already lost the benefit of larger pipe so downsizing the suction is in significant?

I'm not trying to cheat, just make a reasonable decision. If it's not going to make a lot of difference then the 2 inch is easier to work with and cheaper. The jet pressure/flow now if fine for what we like. I don't really like a 'hard' jet. I'm currently using a 2 HP Jandy single speed pump. The new one will be 3 HP Circupool. The new pad will be about 75 pipe feet from the spa. About 50 further than it is now. Hence, the large pump.

Last points: I disagree somewhat on the cost difference. 2.5 inch pipe and fittings are not available at the big box stores and irrigation houses are $15 and up for a fitting. I'm looking at a $100k addition project so every $$ counts here. This isn't about the pool at this point, it's about the addition. The pool will get some TLC a couple of years down the road once the pocket book recovers. I just need to keep it swimmable and a enjoyable as possible until I can get a remodel. I am investing in the new pump, SWCG, and filter. Lastly, what is VGBA?

 

[mas985]

VGBA = Virginia Graeme Baker Act

How long is the run from the pad to the spa?

What size jet nozzles (1/4", 3/8", 7/16", 1/2")?

What kind of filter and heater will you be using?

Where I'm exposing the pipes to do the reroute is not all the way back to the spa, so sizing the returns is not an option. (Maybe in a few years when I get a remodel.) Being that the return is 2 inch dose that change anything? i.e. Have I already lost the benefit of larger pipe so downsizing the suction is in significant?

So you are only planning to replace part of the plumbing? How much are you replacing vs leaving the same?

When we use the spa, the valves are switch to all spa, so it is essentially a dedicated pump at that point.

Does the water still go through the filter and heater? They add quite a bit of head loss.

 

[MouseMan54]

I will be using the Circupool 180 SqFt cartridge filter and I have a 399BTU Jandy XL (XT?) natural gas heater.

When the spa is on, yes it goes through the filter and heater. I have consider adding valves and and a bypass for when we are running the spa.

Not sure on the jet nozzle sizes. Some are missing. The ones that are there look like 1/2". (Side note. As I hinted, the pool itself needs some TLC. I've love to invest more in it now, but every dollar I spend on the pool is a dollar I can't spend on the addition. The addition is the priority as we are moving into a multi generational living situation. As much as I know we love our pools, I love my mom more. So the needs of the addition come first.) The only reason I'm moving the pool equipment is because it is sitting where the addition will be.

Total pipe length to the spa will be about 75'. I'm in southern CA. Our jurisdiction adopts the International Building Code. Not sure if there is something more specific to pools.

 

[mas985]

How much of the 2.5" suction pipe are you replacing with 2"? All 75'?

Also if you have 1/2" nozzles, they require 25 gpm each so I doubt they are that big. The nozzle is inside the jet, not the exterior eyeball.

 

[MouseMan54]

About 60 feet of the suction would be down sized to 2". The new pad will be about 2' higher elevation than the current. Which is about level with the water surface of the spa.


So this is the collar and the 'eyeball' of the jets I have. The pipes behind the socket is 3/4" for each jet.

 

[mas985]

That js the exterior eyeball, not the jet nozzle. The jet nozzle is inside the spa wall. If you look inside the pipe, you can see it.

Replacing that much pipe with 2" is going to significantly increase suction head both reducing flow rates and increasing the likelihood of suction side air leaks.

One alternative to 2.5" is to use 2x2" pipes.

 

[MouseMan54]

Thanks for the input. I'll most likely keep it 2.5. I just thinking in terms of bottlenecks/choke points, since it was only 2" going back. I know adding the length was going to have an impact so may as well minimize as much as I can.

Thanks again.

 

[MinerJason]

Last points: I disagree somewhat on the cost difference. 2.5 inch pipe and fittings are not available at the big box stores and irrigation houses are $15 and up for a fitting.

Shop around or buy online. The 2.5" Sched 40 fittings shouldn't be more than $2-3 for couplings and $4-5 for elbows and other standard fittings. Maybe see if you have a plumbing supply place nearby rather than irrigation supply.

2-1/2" Schedule 40 PVC Coupling 429-025