Water Main Pressure Reducing Valve Clarification Please

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by jim dandy, Mar 21, 2014.

  1. jim dandy

    jim dandy New Member

    Messages:
    18
    Location:
    Florida
    Exterior water main is 3/4 inch PVC (not CPVC). Want to get the best volume of water flow through the valve as I can by using one of these two Watts Pressure Reducing Valves.

    Problem: Either I used the wrong valve to begin with (LF25AUB-Z3) or the valve is defective. There is no external leaks at the valve. Valve set to 55 psi at time of installation. Pressure build to 55 psi but once the water hose water bib is opened the volume drops off more than I like. It acts like the valve is restricted in some way and not allowing full volume of water to pass through it? Now the PRV will not adjust down and is putting out full water main pressure of 61 lbs psi. Current valve is about 1 1/2 year old.

    1) Using a 3/4 inch LFU5B-Z3 or use an adapter fitting to use a 1 inch LFU5B -Z3. Will one of the two valves allow more water to flow through it than the other?

    2) Will a 3/4 inch LFU5B-Z3 PRV allow more water to flow through it than a 3/4 inch LF25AUB-Z3 PRV ?

    Thank You
  2. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,020
    Location:
    Cave Creek, Arizona
    quote; putting out full water main pressure of 61 lbs psi.

    At 61 psi, WHY are you wasting time and money with a PRV? We have PVC mains with 100+ psi but we put the PRV at the house, NOT ahead of the PVC main, and do not "blow out" the piping or have any other "pressure related" issues with it.
  3. jim dandy

    jim dandy New Member

    Messages:
    18
    Location:
    Florida
    The main line pressure has spiked to a little over 70 psi over a 24 hour period of time. I am told the code here is 80 psi a regulator is required, still under I know. Although this house is only 8 years old it was not a quality built house and I am concerned with the water main piping under the house slab coming apart. Being PVC I am guessing that it has couplings connecting the thengths of pipe? I have heard of people having had this happen to their house in other develpoments and want to try to avoid that if I can.

    Another note: I know for a fact that the PVC piping from the outside water meter to the house, about 40 feet is schedule 20 not schedule 40 like I think it should have been. Thus my concerns about the PRV etc.

    Thank you for getting back to me..........
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,258
    Location:
    New England
    PVC is available in many configurations, one way to have problems is if they use drainage pipe as water supply...if the pipe is installed as designed, you should not have an issue with the pressures you are seeing. Dropping it from say 70 to 55psi isn't really buying you much of anything.
  5. jim dandy

    jim dandy New Member

    Messages:
    18
    Location:
    Florida
    Yes I agree with what you say as I thought the same thing since a new correct PRV could end up costing around $300 if not more just for the PRV
  6. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,020
    Location:
    Cave Creek, Arizona
    IF the plumbing was installed even slightly correctly, there is NO PVC under the slab and definitely NO connections. Doing either would have violated EVERY plumbing code in the USA. "Schedule 20" is used for irrigation sprinkler systems, NOT main water supplies, unless your contractor was saving every penny he could to make a higher profit on the house. If it breaks, it will seldom be a pressure issue, but more the result of a "poor installation".
  7. jim dandy

    jim dandy New Member

    Messages:
    18
    Location:
    Florida
    Thank you for your comment. I know for a fact that all the plumbing under the concrete slab is either CPVC or PVC, I have seen it but don't recall if it was CPVC or PVC, I think it may have been a mix of PVC & CPVC ????

    I was present when the builders plumber hooked up the next door neighbors exterior water meter and had to make up the meter to the underground water piping the builders plumber put in and both myself and the plumber shook our heads when we saw the schedule 20 PVC which I have a sample of. This is why I have my concerns about the water pressure going into the house. Under normal correct professional plumbing work I would not have any concerns with this but that is not the case here in Cascades in Saint Augustine Florida. I know for a fact that my water main from the outside water meter as it goes to the house is schedule 20 PVC (about 40 feet long). I don't know if that is code here in Florida but on Monday I am going to find out.
    Last edited: Mar 22, 2014
  8. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,383
    Location:
    Yakima WA
    PVC and CPVC do not mate. CPVC is only used on the interior of a house, and the inside diameter is about 1 size less than PVC. You stated in you original question you were concerned about flow. You don't increase flow with a pressure reducer valve. If your plumbing is as you describe, you may be looking at some changes. Since you aren't really familiar with what you have, it would be my suggestion to get a qualified, licensed plumber to evaluate what you have and advise you on what you should do. It does not seem to me that you need a PRV.
  9. jim dandy

    jim dandy New Member

    Messages:
    18
    Location:
    Florida
    Thank you for your comment. I don't think you understood some of what I question. I know PVC and CPVC don't mate up but you can make it up by using a threaded adaptor. I don't need a qualified plumber because it was a licensed plumber that put schedule 20 PVC from the water meter to the house when it should have been schedule 40 code violation but didn't learn of it until a few years later.

    Code here is at 80 lbs main water pressure requires a PRV. Considering I have at time 71 lbs psi main line pressure and the fact that the wrong size PVC (thinner) was used and considering that the workmanship by the so called licensed plumber did horrible work here I figured I had better use as much caution as I can. I know what I am doing.

    According to code I do not require a PRV, but now knowing other things about this plumbing job by a plumber has me very concerned.

    All I want to know as it pertains to volume of flow is if a 3/4 inch PRV inlet of a Watts LF U5B-Z3 will have the same volume of water flow through the valve as that of a 1 inch inlet PRV of the same make and general model.
    Last edited: Mar 22, 2014
  10. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,383
    Location:
    Yakima WA
    You get more flow from large pipe. If you are so concerned about the Schedule 20 PVC, it's only 40 feet, dig a new trench and put in 1" copper. Yeah, it's more expensive than PVC, but it will darn sure last longer. This is the rolled copper, so it would not have joints. It would have to be brazed at both ends, not soldered. If you still want a PRV, then you will need an expansion tank installed also.
  11. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,258
    Location:
    New England
    A larger PRV MIGHT provide better flow. On some, it's just the size of the fittings and the interior is the same. IOW, you really have to read the specs to determine max flow and pressure drop across them.
  12. jim mills

    jim mills New Member

    Messages:
    141
    Location:
    nebraska
    Actually there is a BIG difference in flow between different valves of the same fitting size. The U5B is typically my go to residential valve, but with PRV's, one size doesnt fit all. There is lots of info & charts on Watts website on how to pick a valve. Also, call their customer help line, they are quite "consumer" friendly & will help.
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