One Well for Two Homes

Discussion in 'Pumps and Tanks Well Forum & Blog' started by molo, Jun 27, 2007.

  1. molo

    molo New Member

    Messages:
    840
    Location:
    cold new york
    Hello All,
    This is my first post to the pumps and wells forum. I would like to build a second home on my property. I have a well.
    1. Can I use the same well for the new home?
    2. How do I find out if the well/pump are sufficient?
    I've read several posts in this forum, and I know there are some well professionals here, I would be grateful for their input and help.
    Thanks in Advance,
    Molo
    Last edited: Jun 27, 2007
  2. valveman

    valveman Moderator Staff Member

    Messages:
    4,387
    Location:
    Lubbock, Texas
    I have a 4 GPM well with a little storage that supplies 3 homes. Even a 1 GPM well can supply 3 homes if you have enough storage tanks. A 10 GPM well can supply 2 homes with very little pressure tank storage. See how much the well will make in GPM on a 24 hour basis and you will know what you need. Size of pump and depth of well, and do a well and pump test. Test the well by running a wide open valve or pipe. Test the pump by running a valve or faucet that holds back about 40 PSI in the tank.
  3. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    During the driest part of the year (this summer) you should pump the well to determine how much water you can get.

    There are several factors.

    1. The pump may be the limiting factor. Is it a submersible or a jet pump? If a jet, is it deep or shallow well?

    2. What are the size of the bore/casing, depth to standing water, depth to the pump if a submersible, and depth of the well? That will let you figure how much water is in the well for immediate demand.

    3. What is the GPM capacity of the pump?

    4. How much water can you pump out of the well during a sustained pumping period? You could try pumping the well with no pressure at the tank to try to determine maximum capacity of the well.

    5. If the pump is too small to determine the capacity of the well, then you will need to test with a pump that will exceed the capacity of the well, unless the existing pump will exceed the demand of the two houses (see next step).

    6. How much water do you plan to use per day for all uses? A normal household with standard showers and no significant irrigation will use around 70 gallons per person per day. However, if you are putting in multihead showers and showering for 20 minutes at 10 GPM that is 200 gallons per shower. You must determine the demand.

    7. Determine demand (total gallons) for peak periods of 1, 3, 10, 30, and 60 minutes. Be realistic. Shower demand is usually limited by water heater capacity. Very short demands are usually toilets and, 10 minute demands usually showers and watering with a hose. Hourly demands are usually sprinkler systems.

    Suggest trying the following:
    1 minute - 20 gallons - 20 GPM
    3 minutes - 50 gallons - 16.6 GPM
    10 minutes - 120 gallons - 12 GPM
    30 minutes - 300 gallons - 10 GPM

    Restrict irrigation usage to outside the peak hours and 5 GPM maximum demand.

    Put in a pump that will deliver at least 10 GPM at 60 psi and operate between 40 and 60 psi.

    You might set your preload pressure 6 to 10 psi below start pressure to provide a little more margin for the case where the pump comes on when the there is very high demand.

    It would be a good case for a "pressure rate" controller where the pump comes on if the rate of pressure loss in the tank corresponds to a flow rate equal to pump capacity. Some variable speed pumps have controllers that start the pump on high rate of pressure drop.

    If your well and pump will not handle those demands, then work out with more precision.

    Consider the above a starting point.

    You should have a water meter mesauring usage for each house. You can put one if yourself for about $50 each.

    You can have one large tank for both houses, or you can have a tank at each house plus a small one for the pressure switch control near the well. Tank size will depend on one and three minute demands and the capacity of the pump.
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