Loud and solid oscillation.

[RobertH6]

I started my pool up this year (3rd year of owning a pool and doing the startup, older system - late 90's) and I have a new concerning problem.

I have a strong vibration/oscillation happening in the system, and it seems to be either coming from the gas heater or Sta-Rite sand filter.

Only happens when the filter valve is in the "filtration" position and no other position cause the problem.

Tried changing the 2 sharp 90° fittings on the output of the heater to sweeping elbows and eliminated the check valve (temporarily). Also changed the filter sand. This has not altered the vibration/oscillation at all.

The very strong (wake the dead) vibration/oscillation gets worse at 19psi, peaks at 23psi, suddenly stops at 24psi. With 300Lbs of new (#20) sand, nothing has changed, vibration remains. After a healthy backwash, about 17psi of pressure. the vibration/oscillation does not change with just drains open or skimmer AND drains open.

What I know about my equipment: approx. 10,000 gal kidney vinyl liner pool, Sta-Rite T-240BP filter (300lbs sand, just changed sand), 1 1/2" piping, bromine dispenser, check valve, 220Vac pump, gas heater. Installed late 90's, last year, I installed a new liner. 2 drains in deep end, one skimmer, 3 returns.

Any idea what is causing it?

 

[ajw22]

Welcome to TFP.

Can you make a video of your problem and post it on YouTube, marked Public, and post a link to it here?

 

[RobertH6]

Here is a video, the phone does not capture the low frequency (loud) noise the oscillation is creating.

BTW, The dispenser is now on a solid shelf. The temp rubber union is out and a new check valve is in place and the low voltage line that shuts down the heater when the pump stops is now in a 3/8 liquidtight conduit as well. Next I would like to turn the pump 90 degrees and go straight into it vs. the 3ea. - 90 degree elbows at the inlet and take out an elbow on the outlet as well. Using long sweep elbows - schd 40. I also pulled the timer and am controlling it with a relay and a WYZE. (I do PLC automation and injection machine electronic repair for a living, I know how to wire and interface stuff)

With the check valve now installed, the oscillation happens less, but when it is oscillating, it is a very strong vibration/oscillation..

Any other suggestions greatly appreciated.

Oops, the video file is too big for here, I uploaded to Youtube.