Turn on pump without pool cleaner - runs fine
Turn on pump with pool cleaner (automatic (HugBug) or manual) - water flow slows down after a few minutes, to less than a quarter
Unplug pool cleaner while pump is still running - water flow remains slow
Switch off pump for a few seconds and switch on again without pool cleaner - runs fine (although initially it blows out a cloud of green algae that the pool cleaner just picked up off the bottom of the pool)
What's going on here?
The outlet was spitting out bubbles for quite a while, and the water flow would slow down, I thought, as a result.
One day the pump was making a lot of noise and I found it wasn't moving any water. It seemed too much air had got in. The water inside the pump housing was steaming hot.
I got a pool repair company to come in and they replaced a right angled pipe that was cracked that attached to the inlet of the pump housing. It worked better but there were still bubbles.
It got progressively worse again, so I thought I would give it a go and try find were it was sucking in air. I found another cracked joint underneath the pool pump which I replaced. No more bubbles. I assumed this would also fix the water flow problem, but it didn't.
The pump is almost 30 years old so I thought it might be the problem. I took it in to the manufacturer. They tested it out and said it was still ok, but replaced the bearings as there were a bit rusted. They also replaced the impeller as it had worn down slightly and replaced the water diffuser (I think it's called) as it had cracked.
I reattached the pump and it did seem to run better that it did before, but after running it with the pool cleaner for a while the water flow slowed right down again. There was a lot of debris on the bottom of the pool though as the pump had now been disconnected for a quite a few weeks.
I subsequently cleaned out as much as possible and backwashed and rinsed several times. But still the water flow rate goes right down after a while if I have the pool cleaner connected.
It runs fine if i disconnect the pool cleaner. It also runs fine if I bypass the filter and connect the pool cleaner - but then it just circulates the dirt.
It seems a bit of fine debris picked up off the bottom of the pool by the pool cleaner that makes it's way to the filter substantially decreases the flow rate, but a bunch of leaves trapped in the weir basket doesn't.
Also, once I disconnect the pool cleaner, switch off the pump for a few seconds and then back on again, it runs fine. If the flow rate remained low then I would suspect a faulty pump, but this just blows my mind. Also, when i switch it back on, it blows out a cloud of green algae (the stuff that it just picked up off the bottom)
Still, the only thing I can think of is a faulty pump as it's so old, but i don't want to fork out more money on a new pump having already had it repaired, if I don't know for sure it's the pump at fault.