Pool spa combo plumbing question.

[PoolChoice]

I have a friend who wants me to help with his pool/spa plumbing.
I am having trouble figuring out, one thing.

He is switching from 2 pumps to 1 pump for a spa/pool combo. The spa has a higher water level.
A check valve on the spa return line would stop the water from draining back, when the spa is off. But what can be done on the suction.
Do I assume the 3 way valve is only going to be on full spa/or full pool.
thanks

 

[JasonLion]

Welcome to TFP!

Typically the suction line is either full pool or full spa, thus no check valve. The return valve is often used in intermediate positions, but not the suction line.

 

[mitch08]

Welcome to TFP!

Typically the suction line is either full pool or full spa, thus no check valve. The return valve is often used in intermediate positions, but not the suction line.

Not to confuse things. But what about this scenerio with a suction valve?

If you are in spa mode. Pulling 100% from spa and returning 100% to spa.
If you have a valve for suction, you can "crack it"... Lets say 5%. So 5% of the water is being sucked from the pool and returned to the spa.

This would allow you to be in spa mode, keep your water heated to where you want it, and at the same time, very slowly refresh your spa with fresh water.

 

[Richard320]

Not to confuse things. But what about this scenerio with a suction valve?

If you are in spa mode. Pulling 100% from spa and returning 100% to spa.
If you have a valve for suction, you can "crack it"... Lets say 5%. So 5% of the water is being sucked from the pool and returned to the spa.

This would allow you to be in spa mode, keep your water heated to where you want it, and at the same time, very slowly refresh your spa with fresh water.

That would work while the pump was on. When the pump is off, the water will seek the same level using the T at the suction valve as the passage between the two bodies of water. But it seems wasteful of heat.

When I use just the spa, I actually suck the spa level down a few inches so there's less water to heat and none will overflow into the pool when we get in. It heats faster that way. It is spa in, spa out. When we're done, things go back to normal, wherein the pump draws only from the pool and returns about 20% to the spa to flush it out and the rest goes to the pool.

When I vacuum the pool, I just about empty the spa into the pool and brush things towards the drain and never need to vacuum it that way. Then I return all the water to the spa while vacuuming the pool. It keeps the cross-currents to the minimum while I'm vacuuming, and no ripples on the surface to obscure the view.

 

[JasonLion]

With 5% coming from the pool you would be running the heater a fair bit to maintain temperature, which you will notice in your gas bill.

The big reason no one does that is that there really isn't any significant advantage to doing so. The spa water gets completely changed out between spa uses anyway.