Adapting a union to a PRV

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by jk60, Mar 16, 2006.

  1. jk60

    jk60 Engineer

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    I have a 1" pressure regulator with a union on the inlet side and a 1" female thread on the outlet side, picture below. My pipes are 3/4" copper so I am using a 1" to 3/4" reducer. In addition to the 1" union hardware, the regulator inadvertently came with hardware for a 3/4" union - see picture. What can I do to adapt this hardware so I can have a union on the outlet side? I am not sure if the proper fittings exist for this mod, and if they do what they are called? Granted I can also use a standard union fitting which is what I have now, but using this hardware just seems like a more "elegant" solution. Thank you ahead of time for any information you can give me.

    Jerry

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  2. Cass

    Cass Plumber

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    You can't do it with what they sent. You can go buy a 3/4" C x C union and sweat it on a peice of pipe and the other end of the pipe with a
    3/4" C X 1"MIP adp. that will screw into the PRV.
  3. jk60

    jk60 Engineer

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    Cass - Thank you for your input. I thought that maybe some adapters are available, but apparently it's a No Go. I already bought a 3/4" C x C Union and a 3/4" C x 1" MIP adapter and will go this way.

    Thanks,

    Jerry
  4. hj

    hj Moderator & Master Plumber Staff Member

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    regulator

    I only buy PRV's with threads for union nuts on both sides, or that come with the unions for both ends.
  5. jk60

    jk60 Engineer

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    Given a chance I would have done the same, especially in view of your previous recommendations for a double union PRV in a thread that I posted a few weeks ago. However I was unable to find the double union configuration at the Big Box stores, and call me cheap, but I am not willing to pay the prices that a plumbing supply house charges. Obviously the cost of hardware at a plumbing supply house to a professional such as yourself is considerably lower then the cost of same hardware to a DIYer. Mind you, I am not complaining, but simply stating the situation from my perspective. There off course is always the option of buying on the internet, but I already returned one PRV that was an internet purchase and did not want to go through this procedure again. I do like improvising and thought I could figure out something "elegant", and if not there was always the fallback option of using a 3/4" C x C union.
  6. hj

    hj Moderator & Master Plumber Staff Member

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    Prv

    And then there is the situation that I would not buy that brand from the "big box" stores, or anywhere else, because it can creater the very situation you are dealing with, plus a much more difficult repair some day in the future.
  7. jk60

    jk60 Engineer

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    If I understand your response correctly, you are saying that you would not recommend the PRV pictured above. If that's the case here is a brief history. I started out with a PRV that was highly recommended - Honeywell Braukmann. After installation I saw that I was dropping up to 18 psi at 8 gpm. That's about three times higher then the spec. Since I originally had a Watts PRV that was somewhat noisy, I decided to give Wilkins a try. With the Wilkins PRV I am dropping about 11 psi at 8 gpm. Also higher then spec, on par with Watts, but not as bad as the Honeywell Braukmann. I also looked at a Cash Acme PRV but the instructions state that it should only be installed horizontally. Mine is a vertical installation. I don't know what other options there were to experiment with but looks like I'll live with what I have now and see what develops.

    Thanks for your help,

    Jerry
  8. Bob NH

    Bob NH In the Trades

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    High Flow Conbraco 36H Regulator

    http://www.conbraco.com/products/ph/techtemplate1.asp?section=B&pid=36H Series

    The 1" Conbraco 36H available from Grainger and others is rated to deliver the following:

    At 25 psi differential the dropoff is 5 psi at 17 GPM.

    For example, if you have 80 psi at the inlet, set the regulated pressure at 55 psi with no flow, the pressure will drop to 50 psi when the flow is 17 GPM.

    If your pressure is lower than 80 psi, you probably don't need a regulator.

    The fall off doesn't vary a lot with differential pressure, so increase the setting if you need higher pressure.

    You might get better performance with your current regualtor if you keep the 1" pipe size for a foot or so before and after the valve, and then use a soldered reducing coupling to go from 1" to 3/4" instead of a sudden reduction.
  9. jk60

    jk60 Engineer

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    Bob - The Conbraco certainly has impressive specs, but the problem I have with specs right now is that they don't seem to work in my house. Realistically neither the Wilkins nor the Honeywell Braukmann lived up to published specs. I have about a 56 psi pressure differential (116 psi inlet/60 psi outlet) and looking at the Honeywell Braukmann specs for a 3/4" D05 regulator, the drop off at 10 gpm and 50 psi differential is only 6 psi, yet what I experienced was an 18 psi drop off at 8 gpm. Similarly for the 1" Wilkins 600 I should only be seeing about a 6.5 psi drop off at 10 gpm and I am seeing 11 psi at 8 gpm. So I am really not sure what is going on, but in view of these results obviously there are no guarantees that even with the Conbraco I would get performance on par with their spec.

    Your suggestion for keeping the 1" pipe size for a foot before and after the valve sounds interesting. I'll have to experiment with that. I probably have just about enough room for 1.5 - 2 feet of 1" pipe on either side of the regulator. I am curious as to what your thinking is on this approach? It's not as if the available volume of water increases much by changing two feet of pipe from 3/4" to 1". Why do you think I would get better performance?

    Thank you,

    Jerry
    Last edited: Mar 17, 2006
  10. Bob NH

    Bob NH In the Trades

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    New Hampshire
    Sharp reductions in area, or elbows, or restrictions near the regulator, can change the pressure within the regulator. It is the pressure within the regulator that controls the regulator. It takes several diameters of pipe to get steady flow and recover steady pressure from the turbulence of restrictions.

    You must be sure to determine the pressure drop across the regulator. Solder a reducing side outlet tee into the 1" line about 6" before the regulator and one just before the reducer after you come out of the regulator. Then put a fitting in to receive two gauges with 1/4" connections (not the hose connector type).

    Check the pressure on the downstream gauge when there is just a little flow (maybe 0.5 GPM). That should be your pressure setting. I don't like to set regulators with zero flow because a little leakage flow can result in a misleading setting. Also, check the pressure on the upstream gauge, which is your utility pressure.

    Now when you run the high flow, see what happens to both gauges. If the upstream gauge drops off, you have losses in your supply piping or meter or shutoff valve. The fall off in your downstream gauge is the result of regulator losses.
  11. jk60

    jk60 Engineer

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    Location:
    San Francisco
    Bob - Thank you for all this information. Here is what I have done previously. First of all the supply pipe from the water meter comes into the house and then branches off in two directions. One branch is the entire house, whereas the other branch is strictly an outside hose bib. This hose bib is not controlled by the pressure regulator and this is where I attached a hose type gage. In standby, the outside pressure is 116 psi. If I turn on a faucet inside the house that has an 8 gpm flow, the outside pressure drops slightly, if my memory serves me right, to about 113 psi. So I think from this it can be said that it is not a supply problem. I have another gauge permanently mounted next to an expansion tank which is next to the water heater. This gauge comes off a 3/4" main line, not a 1/2" branch line. The gauge has a fitting on it, it is not a hose type gage. The pressure readings inside the house that I've reported in the threads above, are taken from that gauge. This gauge is about 50 ft (pipe length - all 3/4") from the regulator. In fact it is at the end of the pipe run, so I assume that readings on this gauge reflect losses in the regulator and probably my pipes. I have also replaced the old shut off valve. What I've installed are two 3/4" full port ball valves on either side of the regulator. With this information my question is - is there enough data here to reach any conclusions or do you still think I need to make provisions for installation of pressure gauges on either side of the regulator?

    Thank you,

    Jerry
    Last edited: Mar 17, 2006
  12. hj

    hj Moderator & Master Plumber Staff Member

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    gauge

    A gauge that is remote from the regulator may not give an accurate reading as to the outlet pressure of the regulator, in a dynamic situation. It will be affected by pipe line losses. When I install a Honeywell regulator and use the gauge on the hose bibb above it, I seldom see more than a negligible drop in pressure when the bathtub is run at full flow. A gauge near the tub however would probably show a sizable drop considering the length of the pipe and that the tub flow is also reducing the latent pressure at that point.
  13. jk60

    jk60 Engineer

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    Location:
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    Thank you hj. Looks like I have some work ahead of me. Still this will make for an interesting and educational project.

    Jerry
  14. jk60

    jk60 Engineer

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    189
    Location:
    San Francisco
    Update

    As suggested by Bob NH and hj, I made provisions for monitoring the water pressure right next to the regulator. Prior to that I had a permanent gauge installed at a distance of about 50 ft of pipe away from the regulator. Since I also have a hose type gauge just for these experiments, I decided to simply install a hose bib next to the regulator. The drop off in water pressure at this hose bib for an 8 gpm flow, was only 4 psi as opposed to 11 psi at the end of my pipe run. So it appears that my losses are primarily in the pipes. Looks like this is something I have to live with, but at least I learned that the regulator was not the culprit in this scenario.
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