No love for PRVs?

ChrisJ

Something has bothered me for well over a year now.....

When you have a PRV on a water service it can be throttling a lot of pressure to keep things nice on the building side. The valve and seat like any other can be easily damaged by grit etc. Only, when even a tiny scratch happens, it will cause the pressure on the building side to slowly climb until it reaches the road side pressure. Which, could in many cases lead to a really bad day.

In my case the high pressure is usually only 88-90 PSI, so it's not really the end of the world, but what about those with 150-200 PSI? That must be fun...

What is typically used to keep debris from getting stuck in the PRV? Pretty much every water filter housing I find is rated for lower pressures and strainers only stop huge objects so they seem to be of some benefit, but it's not a cure.


I've got a feeling most of them are installed without anything really protecting them, but I'm hoping I'm wrong and there's a readily available high pressure filter housing etc.

Jamie Hall

It is a potential problem. However, in most installations, the pressure reducing valve is located on the incoming main and, as such, is subjected -- at least from time to time -- to high enough flows that any fine material should be removed, unless it gets really embedded in a resilient seat material. This is one reason, however, that a PRV -- more so than any other valve -- should be specified with an eye to the maximum flow. You want the velocity across the metering element to be as high as possible, at least from time to time -- and bigger is NOT better.

On the other hand... serious damage can be done to at least some types of PRVs if they are operated close to their minimum flow over long periods of time. This is usually referred to as wire drawing of the seat, and can occur even with very clean water. If there is a very wide variation in flow expected, it may be desirable to use two PRVs in parallel, at slightly different settings, so that one handles only the low flow condition and the other handles higher flows as well.

The long duration very low flow condition is particularly applicable to PRVs used to control the pressure in such applications as hydronic heating systems.

hot_rod

All PRVs I have worked with have some strainer protection. Too small of mesh plugs easily, too coarse allows more debris.
 I suppose a NSF listed Y stained could be installed, but someone would need to service it often if you have debris in the system.

Water meters usually have strainers also, they are often upstream of the PRV and take the first hit of debris.

ChrisJ

hot_rod said:

All PRVs I have worked with have some strainer protection. Too small of mesh plugs easily, too coarse allows more debris.
 I suppose a NSF listed Y stained could be installed, but someone would need to service it often if you have debris in the system.

Water meters usually have strainers also, they are often upstream of the PRV and take the first hit of debris.

If you recall, about a year ago there was a repair done on my line and of course, the house was drained and they opened the curb stop with a slug of mud/rock/sand in the line and it got shot up into the system. It went through the meter fine, damaged the strainer in the PRV and also damaged the PRV. Had I been home, I would've opened the valve I have before the PRV and flushed the line out, but I was working so, it was fun when I got home........

Obviously, that's kind of abusive conditions and hopefully rare, but who's to say it can't happen again whenever work is done on the main etc. It just seems like it could be a bad day if someone has much higher pressure than me.

I was thinking a decent 20 micron filter before the PRV would alleviate such possibilities and likely not clog too often on city water.

I do have a Watts LF777SM1-20 WYE strainer before the PRV now, but that's a pretty coarse mesh in there, I think #20? I believe I tried to contact Watts about a finer mesh, but no dice. Apparently it's available as an option, but that was as far as I got.



Look at that sexy Caleffi PRV....

ChrisJ

P.S. I think that's my boiler water feeder on the shelf behind everything.
That's a good spot for a steam boiler water feeder, I think.

EBEBRATT-Ed

Look at Rosedale Filters in Michigan. I had bought some stuff from them years ago. Extremely helpful and easy to work with.

jumper

I put filter upstream from PRV. Then an unchanged filter does not reduce pressure so badly. Life went on before PRVs got coded in. Fun to make house take off by closing tap real quick.

ChrisJ

jumper said:

I put filter upstream from PRV. Then an unchanged filter does not reduce pressure so badly. Life went on before PRVs got coded in. Fun to make house take off by closing tap real quick.

In my case sure, but what about houses where the pressure is 100-150 psi?  I'm guessing that wasn't possible before prvs?

hot_rod

The strainer in the Caleffi PRV you show surrounds the cartridge in that widest part of the body, so a lot of surface area available.

Excessive line pressure can push particles around, under, alongside the mesh. When we get a return we see the screen distorted from excessive pressure, or a large stone blasts into 

You should be able to find a finer mesh option, be sure the debris is not finding a way around.