PRV causing pressure mayhem (chatter/hammer) during flow

[FixingP]

Hello all.

I’m in the midst of reworking some of my old plumbing, and among the work is replacing a broken PRV. I have installed a new Watts LFX65B (chosen due to space constraints as well as its cartridge-style serviceability…) and have set the static pressure to 60 PSI. My incoming street pressure is 125 PSI.

Now, when I go to turn on a fairly high-flowing outlet, such as my outside hose bib, the new PRV starts to flutter or chatter, causing unstable pressure conditions, pre and post PRV. On the regulated side, the pressure gauge indicates fluttering back and forth +/- 20 psi from ~ 50 psi (which is 10 psi less than the static set point of 60). However on the high side (street side), the pressure gauge gets slammed and is so out of whack that it goes around and around the dial, clicking at each turn! (That gauge is for sure now damaged or mis-calibrated from all the hammering that it no longer indicates the correct incoming 125 PSI when all is static. I have another gauge to confirm street pressure remains at 125 psi.)

Please see this video of the chattering in action:

This does not happing 100% of the time, but I can’t seem to figure out what specifically causes this or what specifically prevents this.

For example, when I slowing open a bath sink faucet, the chatter does not usually happen. However if I do open the same faucet the same way after a chattering incident, then it will most likely resume the chatter mayhem.

The chatter seems to happen most often when I open a high-flowing faucet quickly. I have also caused it to go from no chatter to chatter by opening multiple sink faucets on at a time and then a bath tub spout - resulting in system high flow. However the chatter seems to NOT happen most often (but not 100%) when I open any faucet very slowly or partially.

It seems the PRV needs a “rest” after a chattering incident before I can attempt to slowly open a faucet in order to keep it stable. Opening and closing faucets quickly and rapidly seems to stimulate it to chatter.

The PRV is installed in the correct flow direction.
It is plumbed 1” in and 1” out (no reduction on either end).
I have removed the cartridge to make sure the screen is clean.
All upstream shut-off (full-port ball) valves are fully opened.


Any ideas why this is happening?

Is this PRV malfunctioning or just defective?

Should I get a replacement of the same?

Or should I get a different model / brand / or size?


Thanks in advance.

 

[Dj2]

Try another PRV, it can be the same model. See if a new PRV solves the problem.

 

[Sponsor]

 

[Reach4]

Nice looking system. That oscillation is about 3 Hz, which is slower than I anticipated. I am not a pro.

However on the high side (street side), the pressure gauge gets slammed and is so out of whack that it goes around and around the dial, clicking at each turn!

It seems odd to me that the input pressure oscillation is stronger than the oscillation at the PRV output.

See the reviews, especially the one dated Feb 15 2015 at http://www.homedepot.com/p/Watts-3-...Pressure-Reducing-Valve-3-4-LFX65BU/203473938 which says

After installation however, this unit, when using any one water draw like a toilet, shower, or washing machine, had a resonance/pulsing issue. With pressure gauge attached it would oscillate between 30-50 psi at about 3 pulses per second (whoosh, whoosh, whoosh) and the pipes were shaking around. I talked to HD support who said it could be a restriction in the line to the house, which I tested and ruled out. He said to try another unit, which I did, with the same result. I got the Watts 3/4 LF25AUB-Z3 unit and the problem was fixed.
​

I suggest you have a chat with Watts. http://www.watts.com/pages/contactUs.asp

 

[FixingP]

Hmmm... will get another LFX65B a shot and see if that fixes things. Otherwise will have to consider cutting in (grrrrrrr) another type of PRV. I wonder if it's the cartridge design that causes such problems, and that I should stay away from all other similar cartridge-style PRVs.

 

[FixingP]

Interesting... according to supplyhouse, the LFX65BU was "discontinued by the manufacturer" May 7, 2016. The suggested direct replacement is the LFN55BM.

 

[Dj2]

Manufacturers discontinue products all the time, for different reasons (like slow sales, defective designs among many).
You are not obligated to use Watts, and if you are going to do any cutting and modification - you can use any PRV, except if you have lead free requirement, which have to follow.

Around here, Zurn-Wilkins is the most popular PRV. It could be owned by Watts, I don't know.

 

[FixingP]

I replaced the LFX65BU with the LFN55B-M1. Despite having worse flow curves compared to the X65, the N55 has eliminated the chatter problem in all instances that I tested thus far (high flow, low flow, quick valve open/close, slow valve open, multiple faucets running wide open). Only time will tell as for long-term performance. The body is approx. 1/2" wider, so I was able to reuse the existing sweat unions with minimum other copper surgery to make this fit. Indeed I was ready to go with another brand if the N55 did not work. However I suspect the X65 is not so reliable, considering the problems others have had with it too.