Help with twin undersink filter ID please

I have an 11 year old system comprising two connected housings for cartridge size 10" x 2.5" diam.
The housings are "off white" in color & I'd guess they are moulded in a glass reinforced material maybe nylon?
Each housing has 6 vertical ribs & seals to the top with two full turns compressing a sealing "O" ring.
The housings bear only these markings:
"Made in USA"
"USF - PPI"
One of the housings has failed, presumably due to pressure.
This is unexpected since the installation is protected with an in line PRV, limiting pressure to 130 PSI.
I'd like to determine the manufacturer so that I can get a recommendation about the optimum pressure at which the system should be run.
I suspect the manufacturer was "US Filters" but I can see nothing on any website that looks identical.
Greatly appreciate any help with ID or any other comment.
Thanks.

> protected with an in line PRV, limiting pressure to 130 PSI.

130psi??

Normal faucet pressure is 30-60psi.

Most domestic plumbing is rated 100psi. (Some smaller sizes happen to come out higher, and iron will take more, but the larger sizes of copper or plastic tend to be around 100psi.)

> The housings are "off white" in color & I'd guess they are molded in a glass reinforced material maybe nylon?

There are many specialty housings; see if the FiltersFast gurus have seen such a thing.

For just plain domestic water, the most common is a heavy moulding of PP/ABS/other strong inexpensive plastic without obvious reinforcement. An awful lot of such filter housings are either made-by Pentek (sold under several brands) or are very-very similar.

The spec-sheet for many of Pentek's housings show 125psi for the deluxe models and 100psi or 90psi for the basic ("Big Blue" and natural) models.
http://www.filtersfast.com/All-Pentek-Housings.pdf

I'm not saying you have the standard Pentek, but without other evidence it seems likely that what you have is "equivalent" to standard Penteks. Around 100psi.

If you are ever hitting 130psi, that's over the rating and you can't complain.

It is customary to plumb for twice the working pressure, or to aim the working pressure near half the rating of the pipes (or filters). Since most domestic water is 30psi-60psi, most domestic plumbing is rated 100psi-125psi.

Do you really have 130psi?? That seems excessive.

Could you live with 50psi? Almost everybody does.

I had 60psi and bad pipe-banging, I regulated to 40psi and was much happier.

Do you have water-hammer? A sudden shut-off creates a large fast pressure pulse. The PRV is intended to regulate pressure coming-in, is not good at dumping internal pressure, and is not fast enough to act on water-hammer. There's air-chambers, both at-fixture and whole-house, which soften water-hammer pressure pulses.

The pressure ratings are for "cold" water, under 70 degrees F. The ratings of plastic plumbing drop very quickly at higher temperatures.

Dear PRR
Sorry - I became foolishly confused in making conversions to psi (Australia went metric in 1972 so pressure here is expressed in KPa).
I agree with your general statement about domestic water pressure as found normally in the field.
My PRV (assuming it has not failed) delivers a max of 80 psi (600 KPa), & since I use the needle isolating valve to limit my flow, it's clear the PRV pressure could be lower, but it is non-adjustable.
The local water supply authority say the max supply pressure should not exceed 130 psi. I have heard that sort of vague claim before from supply authorities who often have very poor records of such things.
If indeed I have a Pentek or equivalent with a "max rating" of 125/100 psi (which seems meaningless to me, surely what we all want to know is what is the max recommended working pressure), then I'd agree you would want to limit your pressure to 50/60 psi.
So the indications are in view of the failure that the PRV is inappropriate for this application.
BTW I have again visited Pentek's website & used the link you sent but I can find nothing identical.
Could the markings refer to "US Filters" & if so who are they?
Finally your point about water hammer is well understood although I have no practical experience of measuring peak pressure from this phenomenon. However I'd guess you could expect at least a 50% over pressure spike, when you can hear the pipes banging.
So my problem source could be two-fold.
Many thanks again for your detailed & considered response.

> an 11 year old system

I just opened a filter -cartridge- and the fine print says you MUST replace the sump (canister) every 5 years for clear, 10 years for non-clear.

I did not know that.

It does not say that in the filter housing sales literature, nor in the installer or owner's instructions.

It is reasonable. Plastic has "yield" and is not the best choice for long-term strain; it's just so darn cheap that we certainly can afford to replace one every decade the rest of our life and still come out ahead of Stainless Steel or other "forever" material.

So you may have proved the point.

> My PRV (assuming it has not failed)...
> max of 80 psi (600 KPa)

These can fail. If you have sand and grit, the valve can get blocked-open.

Assuming your PRV is intended to reduce incoming pressure; it may be for blowing-off excess pressure.

> I use the needle isolating valve to limit my flow

That reduces pressure while flowing. When all faucets are off, the pressure will return to full input pressure. If you are washing/drinking 10% of the time, the filter has FULL pressure 90% of the time.

> The local water supply authority say the max supply pressure should not exceed 130 psi.

Hmmmm. Maybe high pressure is the custom in your area. (I recall when Los Angeles was growing up the foothills, the water company bumped the pressure to service new customers, homes down below had pipe troubles until the company zoned the mains pressure by elevation.) And of course, the staff in the office may not know what's really happening in the field.

The fact you feel you need to turn-down a (main?) valve does suggest excess pressure. But what is your pressure?

Can you plumb?

A basic pressure gauge like this is $10.

http://www.homedepot.com/catalog/pro...3498a4_300.jpg
I can't find one in our host's store; this image is from a major US chain-store.

Note that this one only goes to 100psi; it is possible that 130psi will burst out and soak you, so be ready to shut-down. (Air-compressor gauges routinely go over 150psi, but the cheapest sort may not be rated to be wet inside indefinitely. Gauges can be bought from 1psi to 500+psi, but you may have to shop industrial suppliers.)

You may be able to find enough adaptors to fit it to a garden-hose. That might be the best quick check, because it does not require tapping inside pipes and if it bursts you can drop it in the garden and go shut the hose-valve. You might even find a pre-made hose-gauge:
http://www.inspectapedia.com/water/P...r202-DJFss.jpg

It would be interesting to mount such a gauge in the house and watch it as various loads are used, and watch for mains-pressure peaks and sags.

> max of 80 psi (600 KPa),... non-adjustable.

In the USA, we have those on water heaters. If the thermostat fails "on" and the flame runs too long, the tank will burst. Instead the PRV will open and blow-off the pressure... you have water on the floor which is less dangerous than a "boiler explosion". The PRV is the last-ditch safety; ideally it will never open. Looks like this:
http://www.inspectapedia.com/plumbin...ve058-DFss.jpg
That bypasses water heater pressure onto the floor.


There ARE in-line adjustable regulators, a common US brand looks like this:
http://www.inspectapedia.com/water/W...r071-DJFss.jpg
Assuming that the input pressure is greater than the desired pressure, dink the screw on the end, it adjusts from too-weak to too-strong. The gauge is not included, but a good idea.

Bah, why am I typing? This site--

http://www.inspectapedia.com/water/B...-Regulator.htm

--has a (USA-oriented) discussion of water pressure and regulators.

PRR,
Again thanks for the input.
Luckily I have a bit of experience with plumbing hardware & how various items function.
I totally disagree about 10 yearly replacement of the complete housings, two in my case with a twin unit.
For most folks, as for you until today, & myself until a few days ago, I believed these things were properly designed to perform indefinitely (like all plumbing fittings) given that they were installed "within spec".
I had no indication whatever that some secret replacement interval applied, well hidden somewhere in the small print.
And remember you & I can do these things easily ourselves, most people would need to call a plumber & the plumber would safeguard his rear & insist the PRV was replaced also.
Quite some cost all up, & all because someone failed to do a proper engineering evaluation & select a better type of moulding, preferably glass reinforced.
In my case I can see that a modest amount of additional webbing on the outside of the upper cap would have almost certainly prevented this failure, in fact a schoolgirl could see that much.
There is, I am finding, plenty of evidence that these housings are inadequate, & the failure in 2010 (after years of field experience) to offer a practical "max recommended operating pressure" in the spec sheets speaks volumes about the manufacturers attitude, but that of course is IMHO.
By the time I fit decent water hammer protection, & a proper commercially rated PRV, I will fill up the space under the sinkbench & be up for a further $100 or so.
I don't think it matters much what the actual supply pressure peaks are, PRV takes care of that, but a decent fluid filled 0 to 250 pressure guage would be a further $50, nice to have but not necessary.
Now if only I can find who made these damned housings I can vent my feelings at someone who should care.
BTW the local distributors, (there are several all very similar), have little engineering Knowledge & they say whatever they think with little regard to spec sheets or even basic principles. I guess that's what happens when stuff is not safety critical.