Odd issue with a Febco 765

[splitshot]

This is a new unit replaced after last winter's freeze in Feb. Within the last month it has developed a loud hum/vibration when the irrigation is on, which the clients say resonates through the house.
So far I've done this;
Checked the water pressure (65 psi)
Replaced the bonnet and poppet
Replaced one of the 3, 20psi drip regulators (just to eliminate that fail)...

I'm thinking now a weak spring or worn check valve assy? Not common from what I hear.

 

[splitshot]

Follow up for what it's worth.

Replace #14 Spring
&
The check valve assy #'s 15-18.
$34~

From what I've been told, probably the only one on the planet this has happenend to.

 

[titanpat57]

You sure that's a good operating pressure?

 

[splitshot]

You sure that's a good operating pressure?

I 'spose so seems to be the norm in the area (pretty much Tucson in general, anywhere between 45 to 75 psi).

Odd thing is, from everyone I've talked to and from many years working on them, this was a first.

If I were to venture a guess, either the spring or a manufacture flaw on the little tabs that drop into the seat were causing turbulence.

Anyrate, if anyone googles this thread in the future, replace the 2 parts on the left of this pic. Should make everyone happy.

 

[ProE Pro]

Wanted to post a Thank You from Phoenix to the contributors of this thread for helping me fix my valve. Stumbled in here from a google search when our 7 year old backflow preventer started buzzing after landscaping work.

Reviewed the parts breakdown that splitshot posted, then disassembled the valve and buffed out mineral deposits on the Guide and Retainer (parts 17 and 13). Reassembled it, and everything works quietly - saved $25-$45 over buying a kit. If you've got 30 minutes, and the metal isn't corroded, I'd suggest giving this route a try first.