Pump Basket Water Level Drop with Freeze Protection

[Zalligan]

Afternoon All,

Another thread related to the winter weather we received recently. When my pool is in freeze protect mode for extended periods of time, the automated action of the pool switching from pool circulate to spa circulate seems to introduce some air to the system. Typically my pump runs with a few small airpockets up against the top of the lid, however during prolonged freeze protect cycles, water in the basket drops far enough that I can see the incoming water spilling into the pump basket. It hasn't, to my knowledge, dropped to a level that would cause loss of prime, however that is my primary concern.

My current workaround, is to set a schedule to ramp pump speed up to 3000rpm every 4-6 hours to fill the basket back up. My freeze protection pump speed is set to 1650rpms, though I would like to set it lower. Problem is, the lower the pump speed, the greater my issue.

I've tried pulling the guts out of the 3way valve on the inlet side, inspecting orings for damage, and re-lubing them, but this doesn't seem to have alleviated the issue.

Questions are, is this a known effect of freeze protect cycling back and forth, and nothing to worry about as the pump won't get low enough to cavitate barring other issues, or should I start the hunt for what's introducing air during this cycle? For reference, leaving the pool in pool mode at ~1000rpms keeps the basket all the way full, likewise running in spa mode at 2800rpms keeps the pump basket full. It's just the 15 minute cycling back and forth over prolonged periods that seems to be introducing more air than I would expect.

Thanks!

 

[1poolman1]

Afternoon All,

Another thread related to the winter weather we received recently. When my pool is in freeze protect mode for extended periods of time, the automated action of the pool switching from pool circulate to spa circulate seems to introduce some air to the system. Typically my pump runs with a few small airpockets up against the top of the lid, however during prolonged freeze protect cycles, water in the basket drops far enough that I can see the incoming water spilling into the pump basket. It hasn't, to my knowledge, dropped to a level that would cause loss of prime, however that is my primary concern.

My current workaround, is to set a schedule to ramp pump speed up to 3000rpm every 4-6 hours to fill the basket back up. My freeze protection pump speed is set to 1650rpms, though I would like to set it lower. Problem is, the lower the pump speed, the greater my issue.

I've tried pulling the guts out of the 3way valve on the inlet side, inspecting orings for damage, and re-lubing them, but this doesn't seem to have alleviated the issue.

Questions are, is this a known effect of freeze protect cycling back and forth, and nothing to worry about as the pump won't get low enough to cavitate barring other issues, or should I start the hunt for what's introducing air during this cycle? For reference, leaving the pool in pool mode at ~1000rpms keeps the basket all the way full, likewise running in spa mode at 2800rpms keeps the pump basket full. It's just the 15 minute cycling back and forth over prolonged periods that seems to be introducing more air than I would expect.

Thanks!

It is very typical for a VSP that is running at lower speeds to have a basket that isn't full. Happens with or without freeze protection, you're just more aware of what is happening because you're more watchful with the cold weather.
Go much lower and you may not get all the protection you need from the freeze protection. As long as there are no priming issues it isn't a problem.

 

[Zalligan]

It is very typical for a VSP that is running at lower speeds to have a basket that isn't full. Happens with or without freeze protection, you're just more aware of what is happening because you're more watchful with the cold weather.
Go much lower and you may not get all the protection you need from the freeze protection. As long as there are no priming issues it isn't a problem.

Here's the kicker - in the summer i typically run the pump at 1300rpm 24/7 and right now during the winter, running it at 1000rpm 24/7. Pump basket always stays full, as long as there's no switching. So the freeze protection mode is actually running at higher RPM than what I typically run it.

I've confirmed the actuators are rotating the valves correctly (not dead-heading pump). Not sure if a worn out valve could cause this symptom, if it's indicative of a leak somewhere, or what. I never have any wet spots on the pad.

Short of turning the pump off, I think just about any amount of flow would be sufficient for my environment I would think. These cold snaps usually last less than 4 days and don't get below 10. Even at 10gpm which would be a really low pump speed, I think water velocity through the pipes is still ~1fps.

Appreciate the final comment - if it isn't causing problems, it isn't a problem. I might play with cutting back and forth between pool and spa repetitively just to "torture test" and see if it WILL drop low enough to pose problems, or if I'm just being overly protective.

 

[ajw22]

O rings shrink in the cold and leak. That is how we lost the Challenger Space Shuttle.

You have some air leakage in the cold that probably does not show in warmer weather.

Torture testing your diverter valves will just wear the O rings in them faster. All the repeated pool/spa switching every 30 minutes does it 48 times a day and puts more then a month of wear on the diverter every day.

 

[ajw22]

Torture testing your diverter valves will just wear the O rings in them faster. All the repeated pool/spa switching every 30 minutes does it 48 times a day and puts more then a month of wear on the diverter every day.

 

[Zalligan]

Torture testing your diverter valves will just wear the O rings in them faster. All the repeated pool/spa switching every 30 minutes does it 48 times a day and puts more then a month of wear on the diverter every day.

Fair point. So how low is too low in the basket? Assuming seeing it spill in from the inlet is okay, but I’d imagine you wouldn’t want to be able to see the top arch of the outlet/impeller? If it get to that point I’d imagine that would be accompanied with cavitation noises?

 

[ajw22]

Fair point. So how low is too low in the basket? Assuming seeing it spill in from the inlet is okay, but I’d imagine you wouldn’t want to be able to see the top arch of the outlet/impeller? If it get to that point I’d imagine that would be accompanied with cavitation noises?

When it is spitting more air then water.

Easier to watch the size of the air bubbles out of the returns.

When it is spitting air out of the returns up the pump speed for a bit until the pump basket fills. Repeat as necessary.