Pump runs much quieter when solar heating panels are active

riny

Active member
Aug 20, 2020
28
Poughkeepsie, NY
This is an odd one, I think: my (brand new) pump is fairly loud, with a constant high-pitched sort of rattle. I added two solar heating panels with a standard 3-valve bypass, and when I close the bypass and push the water through the heaters... the pump instantly gets much quieter, even though it's obviously working a lot harder. See here:


Any idea what would cause this? The pump is very close to the pool and honestly its job is pretty easy. Maybe this pump just prefers a bit more resistance?
 

cowboycasey

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TFP Guide
Jul 3, 2013
4,430
Fletcher, OK
It sure looks that way, something to do with pressures and things way over my head :)

One thing I will say is going to break your heart.. All those valves that you used are going to break, not if but when... usually within a couple years... I know the Jandy Neverlube valves are spendy but mine I have had 5 years and still turn with ease and if they die all you have to do is unscrew the top and rebuild them...
 

sktn77a

Gold Supporter
May 16, 2010
1,903
Chapel Hill, NC
^ what he said. The pump doesn't have enough back pressure without the solar system in the circuit. It's pumping faster (because of the low back pressure) than the suction side can supply water resulting in cavitation. Could be a restricted/limited suction side plumbing.
 

riny

Active member
Aug 20, 2020
28
Poughkeepsie, NY
It's definitely the pump, you can tell because the noise starts whenever the bypass is open, no matter what position the solar valves are in. The solar panels are a bit uphill so they'll only get water with the bypass closed.

This pool has dual main drains on one 1.5" line and the skimmer on another 1.5" line. If there's not enough pressure, what's the most likely cause? Some obstruction in the lines, or is the pump just oversized for the application? (The equipment is next to the pool at the level of the pool floor, so gravity is doing a lot of the work.)

I'm really upset too because several of my pool-owning friends told me to get a variable-speed pump. I asked my installer about this and he dismissed it out of hand, as overkill and something you'd only consider for a larger inground pool. I didn't know enough to argue with him but now I feel like I should have pushed it. Upgrading to a Pentair SuperFlo VS would only have been a few hundred dollars more, and I wouldn't have minded that relative to the total investment.
 

setsailsoon

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TFP Guide
Oct 25, 2015
3,493
Stuart/FL
When you flow through only two panels you add a lot to the system pressure drop. You see this with the pressure increase on your gauge. This reduces the flow rate significantly and thus the velocities that reduces noise. I don't hear cavitation just normal noise for high flow rates. Cavitation usually sounds like marbles bouncing around in the pump. I agree with the comment above on your valves. When they fail you should consider Jandy never- lube or equivalent. You can also just use the divert valve if your panels are roof mounted. The head difference will prevent water from flowing through them when the single valve is opened.

I hope this helps.

Chris
 

Bama Rambler

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Jun 22, 2009
24,165
SouthWest Alabama
I agree with Chris. That's not cavitation, just velocity induced noise. If you want to stop the noise when not running through the solar panels you can partially close the final discharge valve a bit until the noise stops, or you can change the return eyeball(s) to a smaller size.
 

cowboycasey

Gold Supporter
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Jul 3, 2013
4,430
Fletcher, OK
It's definitely the pump, you can tell because the noise starts whenever the bypass is open, no matter what position the solar valves are in. The solar panels are a bit uphill so they'll only get water with the bypass closed.

This pool has dual main drains on one 1.5" line and the skimmer on another 1.5" line. If there's not enough pressure, what's the most likely cause? Some obstruction in the lines, or is the pump just oversized for the application? (The equipment is next to the pool at the level of the pool floor, so gravity is doing a lot of the work.)

I'm really upset too because several of my pool-owning friends told me to get a variable-speed pump. I asked my installer about this and he dismissed it out of hand, as overkill and something you'd only consider for a larger inground pool. I didn't know enough to argue with him but now I feel like I should have pushed it. Upgrading to a Pentair SuperFlo VS would only have been a few hundred dollars more, and I wouldn't have minded that relative to the total investment.
Well you are in luck because you can go with a VSP pump now and since you have a brand new pump you could probably get away with not changing the pump shaft and seals but I probably would just because... It works very well as I just upgraded this weekend, it took me about an hour from pulling the pump and changing out and reinstalling... I used the 1.65 V green and you have a 1hp also so the 1.65 would fit yours... :)

 

riny

Active member
Aug 20, 2020
28
Poughkeepsie, NY
Thanks all. So what's the consensus, that the noisier operation is normal at such low pressure? I don't care about the noise, you can't really hear it from the pool and it doesn't bother me... I'm only concerned if it's causing increased wear on the pump and could lead to failure.

I might upgrade next year anyway as a VS pump seems to be better for so many reasons. I thought TFP mainly recommended the Pentair?

Here's another silly question: my pump now has a side outlet which works because it's close to the filter, which has a bottom intake. All of the VS pumps seem to have a vertical discharge. What would you do, just come up a bit and then make a U down to the filter? Any issue with three 90s so close together? Here are a couple of pad pics:

20200906_144652.jpg 20200906_144752.jpg