Yeah, but you could take your pool/spa suction valve and close off all suction to the pump and get the same problem. That doesn't mean it has to do with what causes it during normal operation. It might be related, but digging out a new suction line isn't a very convenient solution.
Here's how I see it:
- In spa mode, your pump starts to lose prime in about 30 minutes.
- In pool mode, your pump works fine.
This narrows it down to one of two issues:
- There is a suction leak in the spa plumbing.
- There is too much head for the pump to handle in spa mode.
A big thing that we've all somehow overlooked is your filter. If it's dirty you could have enough suction to run it from the pool but not quite enough from the spa. That could also lead to low flow / gurgling from the heater. Take a hose to your cartridges (or is that a DE filter?) and see how it responds.
Here's how I see it:
- In spa mode, your pump starts to lose prime in about 30 minutes.
- In pool mode, your pump works fine.
This narrows it down to one of two issues:
- There is a suction leak in the spa plumbing.
- There is too much head for the pump to handle in spa mode.
A big thing that we've all somehow overlooked is your filter. If it's dirty you could have enough suction to run it from the pool but not quite enough from the spa. That could also lead to low flow / gurgling from the heater. Take a hose to your cartridges (or is that a DE filter?) and see how it responds.