Blocked return?

[sdbpost]

I just started my second year in this house and the pool has been fine mechanically. Its about 15 years old and the pump motor was replaced before I arrived but never saw this until last Saturday. I switched the suction and return valves to use the spa (first time in about two months) and discovered the pressure gauge on the cartridge filter had jumped from about 12 to over 20, the above ground pipes vibrating and sound of turbulent water near the valve, and there was now a slight crack in the top of the filter housing. I shut off the pump and after replacing the lid on the filter started troubleshooting. In normal operation it appears fine - there are two return jets in the main pool and one in the elevated spa that generates a small waterfall. No vibration or unusual sound.

In spa mode the primary return valve directs all flow into 4 separate jets in the spa. As I slowly moved the valve the pressure started increasing after I passed the halfway point and vibration and turbulence showed up. I stopped moving the valve and checked the output of the 5 spa jets. There was a small, even flow from the 4 spa mode jets and a stronger flow from the main jet (all are the same diameter.) I move the return valve back to main pool mode and pressure returned to normal and vibration and sound disappeared.

I did open the return valve and there was no visible problem. I pushed a plumbers snake into the spa pipe and didn't run into anything in the first five feet. I figured the pipe took a sharp bend at that point and decided not to force it further.

Any ideas? I clean the filter about once a month so I had the system open since the last time we used the spa but nothing unusual happened then or otherwise since then.

 

[HermanTX]

It is common for the filter pressure to increase when in SPA Mode vs. Pool Mode.
The spa jets are small diameter, some or 1/2" for example, vs your pool returns are over 1 inch diameter.
So the spa jets cause more backpressure in the system, thus increasing the pressure at the filter.
The small diameter of the jets in the spa causes the "jetting" action.

Does the vibration remain constant or is it just at start up?

 

[sdbpost]

Now I'm confused. Went out this morning, switched the valve, and no vibration or noise. The pressure jumped to 28-29, but everything else seemed normal. I don't recall ever checking the pressure when in spa mode so I don't know if that is normal for this system, but it seems like that much pressure would be damaging. The only things I did were to replace the filter lid and opened up the valve to inspect the innards.

What is a typical pressure? I've got 2" pipe visible for both suction and return. The pump is a Pentair Whisperflo WF-26 but the motor was replaced a two years ago with a Century B2854 1-1/2 HP, 3450 RPM.

 

[HermanTX]

Every plumbing system at the pad is different because of elbows, bends, etc
If my memory is correct when I had a SS pump, my normal pressure in Pool Mode was around 20-22psi and when in spa mode it jumped to 28-30psi. I have 2 inch plumbing and DE filter.
So I think you are fine.

 

[Jimrahbe]

sdb,

Pressure going up in the Spa mode is to be expected, because all the water has to go through the small spa jets.

But, vibration and noise is not..

I suspect that you have some debris in the line that feeds the spa jets. When the debris clog the jets, there is no where for the water to go, causing the noise and vibration. As the jets cleared, the problem went away.

If the problem returns, you can remove the jets, and then flush out the spa line by running the pump in the spa mode.

Thanks,

Jim R.

 

[sdbpost]

Thanks all. I'll watch the pressure and remove the jets just to check them.