Spa bypass purpose

[jasonhld]

Hi All,

I’m in the middle of re-plumbing for a new pump and decided to fix a hole from an unused chlorine feed that’s been leaking since we bought the house. After I cut the pipe to replace it, I realized I don’t completely understand the flow of the water through the spa bypass.

The attached photo shows the return pipe coming from the pool heater and a diverter that lets us return to the pool or the spa. My question is, what is the purpose of the additional “bypass” loop that has the check valve and shut off valve?

I actually replaced the check valve a little over a year ago and didn’t even think to question why it’s there.

If the shut off valve is to determine how much flow goes to the spa return, couldn’t the diverter valve do the same job just partially turned?

The only scenario I could imagine this being useful for is if I wanted to close of the return completely for some reason, but i’m not sure what the reason would be?

Could this be here solely because a partial diversion of the water would result in hot water being dumped in to the pool instead of being return exclusively to the spa?

 

[mknauss]

Welcome to the forum!

The spa bypass is to be sure a little water is going to the spa to chlorinate it. Can I assume it is a spillover spa? If so, the issue with that is it drives up your pH due to the constant aeration. In automated systems, we recommend using a 'Spillover' mode so that twice a day or so the spa is fully on (flow, not heat) for a certain amount of minutes.

In your case, you can do as you say. Adjust the spa/pool return valve so that a bit goes to the spa all the time and close the bypass.

I suggest you read ABC's of Pool Water Chemistry and consider reviewing the entire Pool School eBook.

 

[jasonhld]

Thank you mknauss!

It is a spillover spa - I should put that in my sig. That makes perfect sense! Without the bypass, water would only circulate in the spa when the return was diverted to the spa.

Thank you for the help!

 

[kadavis]

That line isn't a spa bypass, it actually is the way the installer used to put water through the spa. That is why there is control valve and a check valve between the spa line and pool line. If you close the the control valve and open the three way valve (labeled Spa & Pool) you may partially drain the spa when equipment is off. There doesn't appear to be a check valve on the spa line

 

[jasonhld]

@kadavis Should I put a check valve on the spa line?

 

[JoyfulNoise]

Not to pile-on your “to do list” but that (used to be) galvanized gas line is horribly corroded. It either needs to be replaced or throughly cleaned off and sealed with a rust inhibiting paint. I would also dig down below the ground if the pipe is buried and check to see how bad the corrosion is.

 

[jasonhld]

@JoyfulNoise I appreciate the piling! Fortunately, the corroded part of the line is easily accessible and was one of the motivators for the re-plumbing. ( a puncture in the return pipe was leaking all over it for years ) I was told our 14 year old gas heater would die any day now as it's also heavily corroded so I figured I'd wait and replace the heater and the line at the same time, but that thing just keeps on going.