New pool plumbing help

[mas985]

Texas adopted ISPSC and APSP-7 is part of that. Under APSP-7, it specifies the main drain configuration that is acceptable;

ISPSC

Helpful Links Texas Building Code Officials Association ICC Chapters in Texas Pool Safely

www.txpsc.org

https://westfordma.gov/DocumentCenter/View/70/ANSI-Pool-Entrapment-Info-PDF

Even if they allow each MD to have it's own pipe, I would still cross connect the two at the spa as that is a safer configuration.


Also, what size spa jets (nozzle diameter) and/or flow rate requirement?

 

[ajw22]

Texas adopted ISPSC and APSP-7 is part of that. Under APSP-7, it specifies the main drain configuration that is acceptable;

ISPSC

Helpful Links Texas Building Code Officials Association ICC Chapters in Texas Pool Safely

www.txpsc.org

https://westfordma.gov/DocumentCenter/View/70/ANSI-Pool-Entrapment-Info-PDF

View attachment 544127

Even if they allow each MD to have it's own pipe, I would still cross connect the two at the spa as that is a safer configuration.

Isn’t the above ground piping effectively a cross connect?

 

[mas985]

No because of the head loss between the pad and the spa. With the cross connect at the pad, when one of the MDs is blocked, that suction pressure is very close to the pressure at the pump which can hold someone down. However, when the cross connect is very close to the MD and one MD is blocked the pressure is very close to the pressure of the spa water at the other MD so it is much easier to break free of that suction pressure vs the suction pressure at the pump.

I would very surprised if that passed inspection although some inspectors are not all that thorough.

 

[Lampasas1]

Boy, y’all are really against flex pvc. Does it not hold well to the pressures of a pool system, or do the connections fail, or something else?

 

[ajw22]

PVC Repair - Further Reading

www.troublefreepool.com

 

[Lampasas1]

Yikes, how does that even happen?

Looking at the chart on the link you provided, it says the 2” working psi is 60 and burst psi is 175 vs 230 for pvc pipe. That is quite a difference. What is the max working psi in a pool system, or if a pump was dead headed?

 

[ajw22]

What is the max working psi in a pool system, or if a pump was dead headed?

Around 40psi.

A pipe bursting from pressure is rarely the issue.

Flex PVC has less penetration resistance and easier to get a hole in it then rigid PVC.

 

[Lampasas1]

I will address this with the pool installer tomorrow. Thank you for the information and the insight on the pitfalls of flex pvc.

There was some concern about the spa and the how it was plumbed and pipe size. Should the spa drains be combined closer to the spa and have only one spa suction pipe at the pad level? Should I have a bigger size pipe than 2”?

Is there going to be an issue with how the spa and pool returns are configured at the pad?

 

[mas985]

I will address this with the pool installer tomorrow. Thank you for the information and the insight on the pitfalls of flex pvc.

There was some concern about the spa and the how it was plumbed and pipe size. Should the spa drains be combined closer to the spa and have only one spa suction pipe at the pad level? Should I have a bigger size pipe than 2”?

Yes, the MDs should be plumbed together as shown here close to the spa.


The pipe size should be determined by the flow rate through the system. On the suction side of the pump, you don't what to exceed 6'/sec and on the return side 8'/sec. However, for strong spa jets, you want to stay below 6'/sec on both the suction and return side.

But to know what size for sure, I need to know the spa jet orifice size and flow rate requirements. Most jets are 3/8" which require 15 GPM each or 90 GPM for a set of 6. You want at least 2.5" pipe for both the suction and return side.

 

[ajw22]

. Should the spa drains be combined closer to the spa and have only one spa suction pipe at the pad level?

Yes, Mark gave you the references above.

Show us pics of the drains in the spa.

Should I have a bigger size pipe than 2”?

Probably yes.

Is there going to be an issue with how the spa and pool returns are configured at the pad?

You lack a heater bypass.

2” will work but larger will work better.

 

[Bperry]

Yikes, how does that even happen?

Looking at the chart on the link you provided, it says the 2” working psi is 60 and burst psi is 175 vs 230 for pvc pipe. That is quite a difference. What is the max working psi in a pool system, or if a pump was dead headed?

Tree roots, ground shifting/sinking, animals, etc.

 

[Lampasas1]

But to know what size for sure, I need to know the spa jet orifice size and flow rate requirements. Most jets are 3/8" which require 15 GPM each or 90 GPM for a set of 6. You want at least 2.5" pipe for both the suction and return side.

I don’t know that information but will try to get it tomorrow

Me thinking out loud. If the drain is two 2.5” lines going back to the pump, and the pump inlet is 2”, does the 2” diameter at the pump limit the flow more than the pipe size at the drains? I’m sure there is an intelligent explanation for this, but this is how my simple mind thinks. Please excuse my ignorance…I am certainly not an engineer.

Show us pics of the drains in the spa.

The spa is a separate square fiberglass shell that does not have the drains or returns placed yet. I think the plan is to put them at the bottom on opposing walls

You lack a heater bypass

Yes, that has been addressed with the foreman

I’m pretty sure I will need a check valve at the spa return to keep spa from draining down, right? Spa willl be elevated 18” with spillway

 

[ajw22]

The spa is a separate square fiberglass shell that does not have the drains or returns placed yet. I think the plan is to put them at the bottom on opposing walls

Two spa drains should go on the floor feeding one pipe.

Returns should go in the wall.

Find out from the builder or plumber exactly what will be done.

I’m pretty sure I will need a check valve at the spa return to keep spa from draining down, right? Spa willl be elevated 18” with spillway

Yes.

 

[mas985]

Me thinking out loud. If the drain is two 2.5” lines going back to the pump, and the pump inlet is 2”, does the 2” diameter at the pump limit the flow more than the pipe size at the drains? I’m sure there is an intelligent explanation for this, but this is how my simple mind thinks. Please excuse my ignorance…I am certainly not an engineer.

There is no fundamental "limit" to flow rate in pipe, just head loss. Head loss in pipe is related to both the diameter and the length. So while the head loss per foot of 2" pipe is about 2.5x more than 2.5" pipe, a short length of 2" pipe is not all that bad. The biggest issue with smaller pipe, is noise (i.e. velocity).

 

[Lampasas1]

Mas, thank you for the explanation on pipe size/length and pressure. The installer said that he doesn’t like to install more than 6 jets because of diminishing spa effect. If he increases the drain pipe size to 2.5”, then should I be able to increase the amount of jets too? Sounds like there may be other factors such as nozzle type and size.

 

[mas985]

Mas, thank you for the explanation on pipe size/length and pressure. The installer said that he doesn’t like to install more than 6 jets because of diminishing spa effect.

Because he is using pipe that is way too small.

If he increases the drain pipe size to 2.5”, then should I be able to increase the amount of jets too

No. 8x15 gpm jets require at least 3" pipe.

Sounds like there may be other factors such as nozzle type and size.

Filters and heaters reduce flow rate. You are better off with a dedicated jet pump without any filters or heaters.

But all of this can change depending on the type of jet used.

 

[Lampasas1]

But all of this can change depending on the type of jet used

What type of jet would you recommend for this spa set up? I am using a 3 hp vs pump and a 2 hp air blower pump

 

[proavia]

Don’t put the flex PVC under concrete. Have dirt you can dig up if necessary.

"... Have dirt you can dig up if necessary."
Have dirt you can dig up WHEN necessary.

@Lampasas1
Builders use flex PVC because it's easier and cheaper to install for them.
They are long gone when you have issues with the flex PVC.
In addition to the issues others have listed, I thought there were issues with termites as well.
It is better to use regular PVC pipe.

 

[mas985]

Bigger jets = more flow rate = larger pipe = bigger pump or more pumps. But larger jets are more powerful too. So it is a trade off and a matter of person preference.

Also, a properly designed spa does not require a blower. They are noisy and use a lot of energy. PBs tend to use blowers as a crutch because they don't know how to design a spa without one.

I have a 6 jet spa with 3/8" jets, 2.5" pipe and no blower and everything works great. But I also have a separate jet pump so no heater or filter to reduce flow rate.

Get a detailed schematic of exactly what the PB is planning.

This forum gets soooo many posts about spas that have weak jets and most are due poor designs.

 

[Lampasas1]

I am typically not a poster on the few forums I frequent, mostly a lurker. This site has pulled me in and made me want to truly understand the fundamentals of building and maintaining a pool. The willingness of TFP members to help people like myself is incredible. I really appreciate your time spent on explaining concepts so people can have a clearer understanding of the details of pool ownership.