Low Water Volume On Demand- Pipe Size Too Small?

Discussion in 'Pumps and Tanks Well Forum & Blog' started by Chezelle, Mar 4, 2007.

  1. Chezelle

    Chezelle New Member


    Whats the normal size pipe to use for a well system with a 7-8- gpm pump? Is ¾ PVC and ¾ CPVC too small for most of the main line especially after the pressure tank? Where is the best place to drop the pipe size down from the 1 ¼ NPT size at the water pressure tank?

    Here’s my story:

    I recently purchased a 10 year old home that has some issues with low water pressure/volume at the faucets only when 3 or more faucets etc. are used at the same time. To start with the pressure was very erratic and I found the well tank needed to be replaced(10 yrs old, very rusty water from it, and wouldn’t hold any air pressure) so I replaced it with a new 52 gal tank. This helped stabilize the pressure a lot but I still lose a lot of the volume when 3 or more of any faucets, toilets, dishwasher,washer etc are running at the same time. I can be taking a shower and someone flush a toilet and use a water faucet and I’ll lose about 2/3s of my water pressure and volume. I also did a test while looking at the pressure gauge under the house at the pressure tank while we had several faucets opened and it held the pressure very well dropping only slightly so it has to have a restriction in it somewhere.

    Here is some of my water system info:

    My main water line is about 125 feet of ¾ “ PVC pipe that runs from the well pump then under the house to a “T†at the Pressure Tank(The previous owner also said the well was not very deep-maybe 200 feet to add the the above 125 feet). Following the main line past the pressure tank “T†there is a ball valve that converts the pipe size down from ¾ PVC to ¾†CPVC. A few feet later is a 90 degree elbow and a few feet later another 90 degree elbow changing the pipe to a semi-clear line looks like the Culligan Man put in about the same size (3/4†CPVC) running to 3 tall Culligan water treatment tanks(2 water treatment and 1 filter). The run from the pressure tank T to the tanks is about 6 feet. The line coming out of the Culligan tanks is the same size ¾†CPVC to feed the the home.

    Well pump motor pumped about 7.75 gpm measured at the line just before the pressure tank tee when I had it cut open to replace tank.
    Pressure switch set 30/50 psi
    1800 sq ft 1 1/2 story home.

    Thanks for your help,

  2. Raucina

    Raucina Previous member

    The pipe is small, the pressure is set very low and the filters are big restrictors.

    You can raise the pressure, maybe 45 - 65 to get some help, and keep the filters in good shape or bypass them depending on your water quality.

    Perhaps the filter system could be before the pressure tank, which seems a bit small, and another added for more capacity.

    I am guessing some of the filter experts here will have more ideas....
  3. got_nailed

    got_nailed DIY Senior Member

    Pulling the valve assembles out of the faucets and flushing some water through them would help if there full of junk. I have had to do this a few times with good results (a good time to replace washers).

    As far as moving the filter system before the presser tank and the switch that would be a bad idea. It would be better to add a second tank after the filters.

    All of the wells I have dealt with are 1 1/2 or 1 /14 black flex pipe.

    A 45/65 would help a lot and changing the charge in the presser tank.

    Have you tried bypassing the filter system to see if that helps?
  4. Cass

    Cass Plumber

    Most wells in my area are at least 1" pipe coming into the house.
  5. Pumpman

    Pumpman Pump Sales

    So. Cal
    You may notice a difference by raising the pressure, but you're still going to have limited volume. The friction losses for 3/4" PVC at 8 gpm, is about 12 ft./hd. per 100', plus losses for any fittings in the run. I would guess you could be losing about 10 psi from well head to pressure tank.
    As the other posters have stated, your losses are compounded by the water treatment equipment.
    You may help yourself by increasing the line size from well to tank. I try to run pipe the same size as the pump discharge port when the tank is close and increase at least one size if there is some distance between the well and tank.
  6. got_nailed

    got_nailed DIY Senior Member

    I was thinking about this all night at work and if it was me I would bypass the filters for a few hours and see how much that helps. If it gets a lot better with the filters bypassed then I would try putting a second presser tank on the other side of the filters.

    If bypassing your filter helps a lot then you might want to replace your filter system with a newer system. The filter system that you have might be rated low on GPM at the presser your running.

    I would also change out your presser switch to 45/65 or 50/70.

    IMO and based off what I have dealt with one of your biggest problems are going to be the size of your pipe coming out of the well and your filters.
  7. Pumpman

    Pumpman Pump Sales

    So. Cal
    I would recommend that you check the max pressures of your treatment equipment before you go jacking pressures any higher.
    I still think that your problem is going to be volume rather than pressure even if you increase pressures.
  8. speedbump

    speedbump Previous member

    Riverview, Fl.
    I agree with Ron, pipe size makes a big difference and the filters are probably the biggest restriction of all. If the filters are ten years old like the home, they may need to be rebedded or replaced. I have found some filter companies like to sell a lot of equipment even when it is not needed. Like the others said, try bypassing them and see what an improvement you get. If you have any in line 10" cartridge filters, I would get rid of them altogether.

Similar Threads: Water Volume
Forum Title Date
Pumps and Tanks Well Forum & Blog well water pressure/volume question Jun 12, 2013
Pumps and Tanks Well Forum & Blog 2 inch Water Well Air Volume Control System Apr 1, 2011
Pumps and Tanks Well Forum & Blog low Water volume/presure Jun 29, 2008
Pumps and Tanks Well Forum & Blog Murky water Dec 11, 2014
Pumps and Tanks Well Forum & Blog Running out of water, 55 ft well Nov 30, 2014

Share This Page