Pressure regulator drop under modest flow

[Jeff H Young]

Assuming a double union the companys make a jumper for use during construction should be available through supplier ( made of pvc should be cheap ) throw that on if your only running 70 psi or so it should be ok for a day or so see how performance is.
a lot of differant ideas , I like using the gage and noting pressure drops myself though Im not so sure what the numbers should be. also you need a place to put the gage I guess on a bib. It be a help to check pressure drop on both sides of regulater too just in case its a problem unrelated to regulator but upstream of it.
My house has an 1 1/2 service and regulator but I reduced it to 1 1/4 reg when replacing a bad regulator. because a 3 bath home with 100 psi I figure why pay more for a bigger reg its been fine last few years

 

[Lifespeed]

Just a quick update on how I'm proceeding with this issue. While there can be no doubt the "fall off" in pressure of this cheap homeowner pressure regulator is a lot (12 - 17 psi is considered acceptable according to statements in their regulator selection guide!), the pipe movement resulting from what I consider to be rather mild water hammer is not acceptable. Going into the crawl space of my house I find the rubber-coated coat hanger cheap hangers are in a U-shape, not even crossed over the top of the pipe. Really not acceptable.

So the re-pipe plumber did a decent job on the plumbing, but the strapping job is horrible. I have hired a plumber to properly secure the entire job using unistrut and cushion clamps to address the pipe movement problem. An expensive, laborious job. But I prefer to do things right, too bad the re-pipe plumber from 8 years ago didn't know how to do all of his job right.

Once the pipes are secured I can probably increase the pressure from 50psi to 55psi, making the pressure fall off from this cheesy regulator more acceptable without slapping my pipes around. Should this not provide acceptable pressure during high flow, I'll revisit the double-balanced piston style 500XL series Zurn regulator. Supposedly it has less fall-off.

 

[Sponsor]

 

[Jeff H Young]

A "homeowner regulater" should have worked but evedently you suspect its not good enough. We call the strapping wire hooks . they work ok in most circumstances but if they cross the hold better. the unistrut along with cush clamps is an excellent support/ method very clean Ive seen that in houses lets see exactly zero times. but you have good taste it will be very good , let us know again how everything turns out. ie if reg is ok or changing it helps . very frustrating having bad work good luck

 

[Lifespeed]

I don't just suspect, I measured the pressure regulator "fall off" at 14psi with a reasonable 7gpm flow. Apparently the regulator manufacturer considers this OK. Dropping from 50psi to 36psi is pretty noticeable, but dropping from 55psi to 39psi will be less annoying if the (properly secured) pipes don't bang around from the slight increase in water hammer. I was limiting the pressure to the house as it seemed to improve water hammer, when the real culprit was sloppy strapping.

I know the unistrut clamp approach is not common in houses. But the improperly-installed wire hooks aren't a winner, and I'm not going to spend plumber labor money on re-installing them "properly" by crossing them above the pipe. Once significant money is involved it's going to be done the right way, as I already have poor strapping without additional spending.

 

[Lifespeed]

The plumbing system is properly secured. The water hammer from one hose bib irrigation valve was still extreme after securing the pipes with the cause remaining elusive. It turns out the 25' long straight run of 3/4" copper formed a resonant column, amplifying the shock wave. Re-orienting the hammer arrester from the usual opposed-to-the-valve position to opposed to the long pipe provided the last bit of the solution.

Now I'll turn the pressure up to 55psi and see if it will maintain 41psi after the regulator "fall off". I may be able to live with that, which is cheaper than the better Zurn regulator. Although the unistrut cushion clamp strapping wasn't too cheap. The whole system looks like this, my plumber did a good job. And I paid the price

 

[Reach4]

Glad you succeed.

Re-orienting the hammer arrester from the usual opposed-to-the-valve position to opposed to the long pipe provided the last bit of the solution.

I did not follow that part.

 

[Lifespeed]

Arrester opposed to the valve:

Arrester opposed to the long pipe:

 

[Jeff H Young]

The plumbing system is properly secured. The water hammer from one hose bib irrigation valve was still extreme after securing the pipes with the cause remaining elusive. It turns out the 25' long straight run of 3/4" copper formed a resonant column, amplifying the shock wave. Re-orienting the hammer arrester from the usual opposed-to-the-valve position to opposed to the long pipe provided the last bit of the solution.

Now I'll turn the pressure up to 55psi and see if it will maintain 41psi after the regulator "fall off". I may be able to live with that, which is cheaper than the better Zurn regulator. Although the unistrut cushion clamp strapping wasn't too cheap. The whole system looks like this, my plumber did a good job. And I paid the price

View attachment 67023

That looks real good I like it. Thats good work and not common to see that on a home! Sorry the hammer continues , I belive there is an issue with volume and hard to articulate as its prtly guesswork I have. removing regulator and running without it assuming pressure isnt super high would tell a lot but all this trial and error is consuming of time and costly if hired out. I just dont belive its caused by a cheap regulator but that too is just my guess and admitedly no more valid than yours.

 

[Lifespeed]

That looks real good I like it. Thats good work and not common to see that on a home! Sorry the hammer continues , I belive there is an issue with volume and hard to articulate as its prtly guesswork I have. removing regulator and running without it assuming pressure isnt super high would tell a lot but all this trial and error is consuming of time and costly if hired out. I just dont belive its caused by a cheap regulator but that too is just my guess and admitedly no more valid than yours.

Again, there was no guessing involved on my end. I measured the pressure into the regulator static and under flow, posted above. The pressure drop under flow is solely caused by the regulator, and Zurn cops to this when they state "12-17psi of fall off is normal", as well as when they describe their 500XL model double-piston regulator as being "low fall-off".

The water hammer is vastly improved by the better strapping and the re-orientation of the arrester. It will never be zero.

 

[Jeff H Young]

Might as well change regulators , if thats your problem.

 

[Lifespeed]

Improving the water hammer issue allowed me to up the pressure a few psi, which seems to be enough that I don't hate it so much. 500XL ain't no $80 dollar pressure regulator, either.

 

[canoeguy]

I know this thread is old, but wanted to add:
I have the exact same issue. At 5 gpm, a new NR3XL has an 11 psi falloff-much higher than spec. Also higher than their excel calculator allows. I tried a new 3/4" Watts regulator, and it was even worse, at 15 psi falloff. None of these units come close to meeting spec, and that seems to be the way the industry functions. It's a real PITA because I'm trying to design an irrigation system, and can't engineer it without reliable specs. Maybe the 500XL has more realistic specs. I doubt commercial users paying $500+ for the unit are going to put up with this.
Note that "falloff" isn't just one line though. If you look at Plast-o-matic regulator spec sheets, there's a hysterisis shown. Falloff changes significantly depending on whether flow is increasing or decreasing. (note that those regulators cost $2300+ for a 3/4").
Zurn is probably showing the best part of that curve, and not the other side. That accounts for some of the discrepancy, but certainly not all of it.

 

[Fitter30]

Did you read the spec sheet 80 psi minimum. Regulator 5lbs, carbon filter 5lbs, water softer 7-10 lbs, water heater 10lbs all depends brand and model.

https://s3.amazonaws.com/s3.supplyhouse.com/product_files/1-NR3XL%20-%20Submittal.pdf