We have a Hot Spring hot tub, about 10 years old. Two pumps control the jets. (A separate pump controls the heater, which is working fine.)
Here’s the problem we’re having:
When you turn on the jets, they pump at about 50% for about a minute, and then gradually lose power. After about 5 minutes, they’re down to about 10%, where they stay. Both pumps do the same thing, and lose power at the same rate.
If you turn the jets off for about 10 minutes, they go back to the stronger then weaker cycle.
This same problem occurred several months ago, and spontaneously fixed itself, but now it’s back.
The filters are fine, and running it without the filters doesn’t fix the problem.
We seem to be getting normal power (tested with a mulitmeter) into the power panel.
Check the discharge port / nozzle where the water/ozone enters the tub. Mine had hard water stuff clogging it. Opened it up by removing screws, cleaned and it worked fine.
Also, check the (most likely) common suction side of the two pumps. Sounds like you may have a leak allowing air to be induced (sucked in), causing cavitation and loss of flow.
If this was the case, would water be leaking out, or would somehow air just be getting in? We don’t seem to be losing water, and there are no obvious leaks in the pump area.
I haven’t had time to do anymore trouble shooting on this yet. We’re going to drain the tub this weekend and try to find any hard water deposits that might be causing this.
I don’t know about hot tubs, but what you are describing is exactly what happens when you have debris meeting a filter or other restriction.
The fluid gets sucked through the filter and gradually the debris builds up, stuck to the filter. Eventually the filter is completely blocked. Shut it off for a few minutes and the debris falls away and things are good to go again for a while.
Anybody that has tried to drive an old car with junk the gas tank has had this happen. The car will start and drive… stutter and die…start right back up and drive for a while.
Thanks. I’m wondering if there is a filter in this system that we don’t know about and that isn’t easily accessed. There are 5 big filters in the tub itself, but maybe there’s another one I’m not seeing. I’ll try to figure it out.
With the pumps turned off you’d probably be able to see a suction side leak. With the symptoms you’re describing, it would likely be a significant leak, assuming that’s the problem.
Have you watched the skimmer area while it’s running at 10% power? Is the filter/skimmer area going dry? Sometimes an older skimmer weir can get stuck, preventing enough water from reaching the pumps
Has the hot tub run at all with a filter not installed? I’ve seen clothing sucked into the plumbing, which caused problems similar to what you’re describing.
When you drain it this weekend, perhaps try removing the large nut on the front side of the pump (WITH THE ELECTRICITY TURNED OFF) and check for any type of obstruction at the impeller. You should be able to spin the impeller fairly easily by hand.
In this case, you would most likely see evidence of a leak (H2O out) when the pump is off, but not necessarily. Sometimes it doesn’t take much, evidenced merely by a damp spot underneath, to cause air intrusion on the suction side and then cavitation and loss of flow.
Just an idea to look at, no implication that it’s THE solution. Lots of good (perhaps better) ideas here too. Look for the easy/obvious solutions first… 90% of the time, that’s where it’s at.