very low flow in new home....

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by rtstephn, Jun 13, 2008.

  1. rtstephn

    rtstephn New Member

    Messages:
    18
    Hi all,
    First time posting. I am building a new home and just finished my plumbing trim out. I have noticed before now (but it's now painfully apparent), that I have issues with water pressure. Pressure is very good when I first turn on the tap, but fades dramatically within 15 seconds or so. I tested the water pressure at an outside spicket and have 80 PSI static pressure, but if I turn on another spicket, then it drops to below 15 PSI. If I turn it all off and wait 30 seconds or so, it builds back up to 80 PSI.

    On the advice of local building inspector, I ran 1'' pex from 3/4'' meter to my house, some 525 feet away (with about 275' going up hill). PEX is run throughout the house.

    I called in a service plumber, and he told me that I needed a larger meter valve (2''). I called the city water engineer, and he told me I did NOT need a larger meter, but I did need to run 2'' PEX to my home.

    At this point, the expense is too great to run new pipe (assuming this would fix it, the plumbing I called in didn't think so....). Do I need a booster pump? Or do I need a booster pump and some kind of tank for on demand water? What do you recommend I do now. The house is now nearly complete and ready to move in (except for water pressure issue).

    Any help would be very much appreciated.
  2. Terry

    Terry Administrator Staff Member

    Messages:
    15,289
    Location:
    Bothell, Washington
    The meter can stay the same.
    The pipe should have been larger.
    Right now you have the equivalent of sucking a milk shake through of coffee stirrer.
    525 feet should have been something large like 2"
    It's not a booster pump you need, the pressure is already at 80 PSI
    You need to store water to be used later.
    Choices are,
    Run a bigger line
    or add storage tanks.
    Last edited: Jun 14, 2008
  3. do the booster tank...

    2 inch seems like an extremely large line
    to run for a home, even at a distance like that....

    one inch or 1 1/4 should have been large enough..

    at least in our area....


    I probably would have made the same mistake myself...


    I suppose your best bet is to put in a large well-x-trol baldder tank in the mechanical room...

    try that first before anything else..
  4. rtstephn

    rtstephn New Member

    Messages:
    18
    What tank do you recommend....

    THanks for the reply. What tank would you all recommend? Do I need a certain size....it's only my wife and I and we are gone during the day...though we hope to grow the family at some point.

    Would I just need a tank, or would I need a pump also?

    Thanks much,
  5. leejosepho

    leejosepho DIY scratch-pad engineer

    It seems to me that a very large bladder tank could keep the pressure relatively steady for the duration of a normal shower, but then it would take *much* more than 30 seconds for the overall system pressure to again build to 80 ... and who knows how many toilets or washers will be sitting with open valves and waiting for water at the same time.

    I would add a small pump-and-CSV combination set to come on around 50 and maintain 60 until the pressure switch again shut it off at 70.
  6. rtstephn

    rtstephn New Member

    Messages:
    18
    -



    So I don't need a pressure booster, even though pressure drops after initial "burst" of water. What kind of storage tank? I am guessing that the pressure is dropping because there is not enough volume to sustain it. Is that right? So If I add volume (by adding some kind of tank), then I would increase available volume and therefore the pressure would remain high? IS that right, or am I reading too much into your post!?
    I wish I could go back on the building inspector for recommending a 1''.
    THanks much.
    Last edited: Jun 14, 2008
  7. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    Like Terry said in the first reply, you need a bladder tank.

    You want to store as much water as you can so you want to keep the supply pressure at 80 psi, and you need a tank that has a large acceptance volume.

    Let's assume that you want at least 40 psi for your normal flow. Precharge the tank to 40 psi and it will fill to 80 psi when there is no demand (which is most of the time).

    If the precharge is 40 psi and the fill pressure from the utility is 80 psi, then the tank will be 42% full of water when the pressure is 80 psi.

    You must get at tank that has an acceptance factor of at least 42% or you will damage the bladder. Most will work but some won't.

    An 80 gallon tank will give you 33 gallons of storage and a 119 gallon tank will give you 50 gallons of storage. In addition, the supply will provide some makeup while you are using water. Here I am talking about ACTUAL VOLUME of the tank; NOT "equivalent" volume.

    An 80 gallon tank (33 gallons drawdown) will be plenty for 2 people.

    Multiple tanks with total capacity work the same as one tank but take more room and a bit more plumbing. Consider the cost per installed gallon when comparing tanks of the same quality. Here are a couple of sources of tanks.
    http://www.wwpp.us/wellmate/wm-tank.shtml

    You need a tank with a bladder that will not be affected by chlorine. I know that the Wellmate tank with a polyethylene liner will survive the chlorine levels in municipal water.

    You don't need a tank-tee kit because you aren't using a pump with pressure switch and relief valve. It will be installed with just a plumbing tee.

    If you don't like the pressure swings you can install a regulator set at maybe 50 psi AFTER the tank. The pressure loss in the regulator will affect the available pressure a little but not much. I would hold that until you see if there is a problem with pressure variation.
    Last edited by a moderator: Jul 10, 2011
  8. rtstephn

    rtstephn New Member

    Messages:
    18
    So what would you think of the of WellMate WM-25WB
    87 Gallon Tank from http://www.wwpp.us/wellmate/wm-tank.shtml
    This would give me 26 gallons drawdown at 30/50.

    Is this enough? Just from browsing the web abit, I'm pretty impressed with Wellmate. Their prices are super competitive.
  9. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    The 30/50 drawdown of 26 gallons has no meaning with your system. That is the drawdown for a pump with a pressure switch setting of 30 and 50 psi start/stop.

    The 87 gallon tank will have about 36 gallons "drawdown" from 80 to 40 psi operating range as I described.

    I would precharge it to the lowest pressure at which you want good flow unaffected by the pressure loss in the long pipe from the meter. I suggest 40 psi. If you use enough water to empty the tank then you will still get water but at low flow rate until the tank can recover at the flow rate available from the meter.
  10. rtstephn

    rtstephn New Member

    Messages:
    18
    Oh, that makes sense, I was thinking those numbers were dynamic vs static pressure. Thanks for the clarification. Would I be shortening the life of this product the tank would have 80 PSI on it most of the time (when no water demand). Also, what kind of pressure swings will I have. Will it be noticible in a typical shower? Or will the pressure swing only start to happen as the tank is depleted of water.

    Thanks so much for the guidance here. I feel much better about the prospects.
  11. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,026
    Location:
    Cave Creek, Arizona
    System

    Your supply line can only supply a finite amount of water so if you were to put a pump at the house it could suck the pipe dry and not give any additonal water. A diaphragm tank will supply the volume you need and the city line will keep it pressurized. You would have diminished pressure once the tank was empty and then had to rely on the original volume of water for your usage, but with a large enough tank that should not occur very often.
  12. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,262
    Location:
    New England
    The pressure would drop from the supply pressure of 80 until the tank's stored energy and water can no longer produce anything, which would be if the overall system pressure dropped to 40 or less. At 40# (assuming that's th evalue you set the precharge in the tank, it can't help push stored water out any longer, and you'd be limited by what's in the supply line. So, you'd never get less than what you have now without a tank, but would get a minimum of 40 (starting at 80) water pressure and volume until the stored water is basically gone. If you reach that point, you can either add more stored water or add a pump to force more into the system, or, produce fairly constant pressure (the end result depends on where you put the pump). I think you'd prefer to avoid the expense in materials and power to avoid a pump unless you can't live with what you have. You're lucky you stilll have 80# at the top of your hill, otherwise, you'd need to add a pump regardless.
  13. somethig is not right here

    it would seem to me that a one inch line should have
    done you ok

    A one inch line can put out literally
    a whole shitload of water...at 80psi

    at least in the mid-west it does....


    I have installed a one inch line for commerical buildings
    before.....

    so....it makes me wonder if you have not kinked or crushed the
    pex line somehow in the process of re-filling the ditch.>>>


    or are you sure that you dont have a bad gate valve at your main stop????
    Last edited: Jun 14, 2008
  14. Redwood

    Redwood Master Plumber

    Messages:
    7,450
    Location:
    Connecticut
    I find myself wondering the same thing!
  15. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    Here is a link to a chart for head loss in ft of water.

    http://www.cozyheat.net/MTR/tubing/pdf/headloss.pdf

    The chart gives the head loss for each 10 ft of pipe (an unusual scale).

    At 5 GPM for 1" PEX the head loss from the chart is 0.35 ft per 10 ft; which is 8 psi loss for 525 ft. That is not too bad and you shouldn't notice it.

    At 10 GPM for 1" PEX the head loss is 1.25 ft per 10 ft and the pressure loss for 525 ft is 28 psi.

    If the line is kinked you will have a hard time finding it until it fails and causes a leak.

    Try to do a bucket flow test to determine the flow rate and pressure at the house. If you get a pressure gauge that goes on a faucet where there is a hose fitting, and then measure the flow at another faucet while reading the pressure, we may be able to suggest something about the pipe.
  16. Redwood

    Redwood Master Plumber

    Messages:
    7,450
    Location:
    Connecticut
    If it is kinked you may be able to locate the kink with an ultrasonic leak detector. It may pick up on the non-linear flow that ocurrs at the kink.
  17. rtstephn

    rtstephn New Member

    Messages:
    18
    So the general wisdom here is that it is unusual to see this much volume loss wiht 1'' pex? I can deal with lower water pressure, but what I have, after the initial "rush" of water, is pretty rediculous. It makes we wonder whether or not I'll pass my final and get my CO. Don't get me wrong, I have more than just a trickle, but it's weak. Like I said in my first post, it goes from 80 PSI static to less than 15 PSI when another tap is opened.

    Is this Ultrasonic leak detector something that I could rent, or would I hire someone to come out and do it. Who usually does something like this?
  18. rtstephn

    rtstephn New Member

    Messages:
    18
    Here is a link to a chart for head loss in ft of water.

    http://www.cozyheat.net/MTR/tubing/pdf/headloss.pdf

    The chart gives the head loss for each 10 ft of pipe (an unusual scale).

    At 5 GPM for 1" PEX the head loss from the chart is 0.35 ft per 10 ft; which is 8 psi loss for 525 ft. That is not too bad and you shouldn't notice it.

    At 10 GPM for 1" PEX the head loss is 1.25 ft per 10 ft and the pressure loss for 525 ft is 28 psi.



    Does the fact that I am going uphill for part of the way affect any of these loss calculations? It is going uphill (not super steap, but uphill nonetheless) for about half the distance. The service plumber I had look at it told me "have you tried pushing 80# up a hill, that's where you are losing your water". But wouldn't I loose some of that 80 PSI that I have at static too then?
  19. Terry

    Terry Administrator Staff Member

    Messages:
    15,289
    Location:
    Bothell, Washington
    600 feet of devolped length, over 60 PSI, not accounting for elevation gain.

    3/4" meter, 1" pipe, 14 units
    3/4" meter, 1-1/4" pipe, 26 units
    1" meter, 1-1/4" pipe, 26 units
    1" meter, 1-1/2" pipe, 51 units

    The standard three bath home requires 34 units.
    UPC table 6-6
    Last edited: Jun 14, 2008
  20. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    A larger line would have been the answer. At 525 feet, 1½" schedule 40 PVC or PE would be adequate. PEX might need to be 2". At this point, storage is really the answer. You mentioned a hill. Keep in mind that each 10 feet of elevation change causes pressure loss of 4.4 PSI. If it is a tall hill, that also has to be factored in.
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