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2 homes on 1 well

robbird's picture

I am building a new home on my property and will convert my current home into a workshop/office. I have a well with a pump hanging in the shaft and a pressure tank in the home. Does anyone know if I can hook up the new home to this well and have 2 pressure tanks, one in each building? How would this be wired? Thanks

(post #110358, reply #1 of 18)

How far away is your new home from the exsistig well head? Pressure tank.

"Some days it's just not worth chewing through the restraints"

(post #110358, reply #2 of 18)

Why two pressure tanks?

You can distribute the water from the tank (actually unless there is a checkvalve any place past the pump discharge) to any place that you want.

All you need is the pressure and flow to handle the loads including a pressure losses in the additional run.

. William the Geezer, the sequel to Billy the Kid - Shoe

(post #110358, reply #3 of 18)

The cabin my wife and I are staying in while I build our house shares a well and pressure tank with the main house it sits near. Our water usage is considerable compared to what I imagine you will have a need for in this conversion and it works just fine. I doubt there would be a need for a separate tank for your converted workshop.

Kevin Halliburton

"I believe that architecture is a pragmatic art. To become art it must be built on a foundation of necessity."  - I.M. Pei -



If we fail to catch a cosmic fish it may be a trillion years before the opportunity comes again

(post #110358, reply #4 of 18)

Bob, the question is "How much water can the pump/well provide?"

If you use more water at one time than the well has available, you need a larger storage tank to maintain a supply. If use stays the same, or within the pumps capability the current tank is sufficient.

Unless the home shop is a carwash?

Joe H

Edited 7/28/2003 8:08:14 PM ET by JoeH

(post #110358, reply #5 of 18)

A few years ago I installed a potable water system for a factory.  It was supplied from wells.  We installed two pressure tanks, one near the wells and one at the other end of the plant.  They were fairly large bladder tanks (several hundred gallons) and were separated by perhaps a thousand feet.

Having tanks in two separate locations did not work well.  It caused oscillation in the pump control.  The pump would kick on, fill the first bladder tank, reach pressure, and turn off.  Meanwhile, the second tank had not yet filled because it took time to get enough water through the line to the second tank.  Water was still flowing into the second tank when the first tank reached pressure and kicked off the pump.  It continued to flow after the pump stopped, trying to equalize pressure, which drew down the pressure in the first tank and kicked the pump back on.  The pump banged on and off a dozen times, sometimes only five seconds apart, before both tanks reached pressure.  We ended up eliminating the far tank, and everything worked fine.

So, I'd recommend a single tank, too large is better than two small, and adequate size pipe throughout the system.

(post #110358, reply #6 of 18)

The new home is about 300 ft. away from the well and I buried 1.25" pipe which was teed into the line going into the existing home which is 1" pipe. I used 1.25" from the pitless adapter, then attached the 1" with a reducer. I believe that I have a 3/4 hp. pump with a 33gal. pressure tank. I tested the water in the new house at the 1.25" line and had good pressure for about 10 -15gal then it trickles to a stop. after about 5-6 seconds it sputters to life- good pressure for 10 gal-trickles to a stop, over and over. In the meantime my wife tells me there is no water in the house until I close the 1.25" valve. My thought is that it is sucking the water out of the pressure tank until it kicks the switch on.  I was advised by a local plumbing guy to switch the tank into the new home when we move in and use the "shop" as a secondary where water will be less of a priority. Is the pressure tank pushing water back toward the well in addition to pushing it toward the fixtures in the house? Does this guy's advice sound like the cheapest yet effective way to go? I'll still have to trench a 220v line to the well but it beats 3k for another well.  Thanks for all responses.

(post #110358, reply #7 of 18)

I'm not sure if this will help, but we faced a similar situation, except that the new home is 2300 feet away.  In our system, I installed a 1200 gallon cistern that draws from the existing well (submersible pump works fine over that distance).  I then installed a submersible pump in the cistern and that pumps to a pressure tank.  Works pretty well.

(post #110358, reply #8 of 18)

Not that it's news to you, but you have a component problem.  

I have a well (with submersible pump) 750' away with a substantial elevation drop.  Due to poor advice I installed the pressure tank and switch in the lower building.  With the proper pump, not just hp rating, I have no problem getting water to the (upper) house.  But I have a 50# pressure drop so am required to run the switch 80/100 psi to get 30/50 at the house.  It works OK but effectively reduces the size of the pressure tank due to the higher pressure.  100 psi at the lower hydrant wakes up the unwary.  If I have a little too much air pressure in my tank I'll experience a slight lag between the tank supplying water and the pump taking up the slack.

My pipe is smaller than yours.  You shouldn't be having a problem if your pump, tank, and switch are working together.  Sounds like the pressure in your tank doesn't match your switch setting.  That 2 psi differential is important.  As the system gets bigger, especially longer, any wrong adjustment becomes more apparent.

Check your pressures.   

PAHS Designer/Builder- Bury it!

PAHS works.  Bury it.

(post #110358, reply #9 of 18)

VaTom had some good insight.  Also, I don't think moving the tank is a bad idea, but it wouldn't be the first thing I'd do, because I don't think it's the real problem.

The water could be going back down the well if the check valve is bad.  But it would happen regardless of where the tank were located.  It would have to be fixed no matter where the tank was.

I'd also check the pump pressure switch settings like VaTom said.  Check that the pressure gauge is good, too.  And check that the tank is working properly.  If it's an old bladderless tank, make sure it's not waterlogged.  If it has a bladder, make sure it doesn't have a hole in it, and that the air charge is correct for the pressure switch settings.  Set per the instructions.

If you still can't find the problem I would not spend $3,000 for a new well.  Hire someone to troubleshoot for you -- it would be cheaper.

Good luck.

(post #110358, reply #11 of 18)

Are you pulling water for the new building off of the line between the pump and the pressure tank?  If yes, that is your problem and you have two solutions to consider.

1) tee off from the old building after the pressure tank.  Think of the new building as another room within the old building.  If you were plumbing a new bathroom in the old building, from where would you get the water? (he asks rhetorically. . .)


2) put a second tank and pressure switch in the new building wired in parallel with the old.  That way, both buildings will use the well pump and will call for water when it's respective pressure tank runs low.

The person that mentioned the problems with the dual pressure tank situation had a pump, into a tank, into another tank.  That (as he recognized) is not a good solution.

Now, the one thing not addressed here is the electrical isolation of the two buildings.  I am sure that someone will chime in on this, but make sure that having the buildings connected by the fantastic earth ground known as a "well" is an OK set up.

Good luck

Steelkilt Lives!

(post #110358, reply #12 of 18)

If the pipe used to connect the two is plastic, there's no conductivity connection, right?  He didn't say what he used, but around here, we don't bury well pipe unless it's plastic.  The earth heaves in the winter and plastic is more flexible. 

Which brings an oh-by-the-way that an electrician should answer, it the pipe connecting the two is plastic, should the water system in the new building be bonded with its only grounding rod, or does it need one at all?

I don't know, just asking.  I've seen it both ways, but that's in the piney woods of Maine (summer camps) where the word 'code' is used to signify that you've got a winter illness.


I never met a tool I didn't like!

"I am the master of my fate, I am the captain of my soul."  Invictus, by Henley.

(post #110358, reply #13 of 18)

That's what I guessed would be an option, to treat the second/main house as a fixture. Then I thought about some pressure delay or problem with having the pressure tank 300-350ft. away. Then I thought about having a second pressure tank w/o a switch. Would this provide pressure and volume for most applications until my wife fills the bath?  Would 2 tanks w/2 switches do anything bad to the tank not needing filling when the other calls for water? The more I consider leaving the future shop as a non-priority water demand I am reminded of possibly needing this building as a future home for aging parents or a mother inlaw. I guess I should get it correct now.

By the way, the tee for the new house is between the well and the existing house, and is run under the frost line with plastic.  Thanks to all.

(post #110358, reply #14 of 18)

If the outbuilding must one day function as it's own residence I suggest that you leave the T where it is (between the well and existing house and pressure tank) and install a second pressure tank and switch in the new building.  I am pretty sure there should also be a checkvalve preventing backflow for/from each tank back into the main feed.  Shared wells are not totally uncommon, ask a well guy about the proper type of valving to use.

You will need to wire the switch in the new house to call for water as if it were it's own well.  The only different part is that the power will continue to come from the existing source in the panel in the old house.  You will be running a lot of distance with that wire (old panel to new pressure switch and back to the well) either oversize it for the voltage drop, or isolate the new pressure switch by doing wiring with an interposing relay.  (i.e., the new pressure switch in the new house will energize a relay located near the old panel and pressure switch)

The only drawback on this is that the volume of the existing pump may not be able to handle both homes asking for full demand at the same time.  I say you cross that bridge (a new pump) if and when you come to it.

The up side is that your existing pipe stays un-touched and all you are burying is wires (which don't need to go down below the freeze line)


Steelkilt Lives!

(post #110358, reply #15 of 18)

We have two homes on one well.  One pressure tank is located in a pump house at the well casing (that's how things are done around here).  Run to second house is tee-ed off the main run just before it enters the first house.

-- What's the flow rate of your well/pump system?  You should have a flow test done.  You should have at least 5gal./minute per house.

-- The water in the first house reduces to a trickle when you open the 1.25" to the second house?  That may not be too surprising.  The flow out of a 1.25" pipe may be too much for the well.  But a residential use shouldn't use that amount of flow.  What happens if you terminate it in a hose bib?

(post #110358, reply #16 of 18)

I haven't tried to reduce it to 3/4 or 1/2 yet. I expect it will improve but will probably have a surging flow as the tee is before the pressure tank. 

Thanks for all replies. They have given me much to consider.

(post #110358, reply #18 of 18)


The picture that I am using to look at your existing system consists of several virtual pressure tanks in series... What I mean is that each of thse 100s' long PVC pipes acts like a pressure tank. So does each house. So, you have 6 pressure tanks and 1 pump.

PTs: 2 houses, 1 PT, 1 pipe from pump to Tee, 2 pipes from Tee.

When designing a water system You have to have the Pressure Vessel and pressure switch at the head of the system. You will have to move the PT back to the well head or at least as near as the Tee.

In order to isolate the 5 VPT's from each other and the real Pressure Vessel, use backflow preventers. Place a backflow preventer at each junction of a virtual pressure tank. I would also place 1 @ 75' of 1.25" and 1 @ 100' of 1" pipe.

In order to prevent oscilations you have to have backflow preventers... in order to feed thru them , the pressure can only come from the system head (the PUMP).



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(post #110358, reply #10 of 18)

I am trying to visualize the setup and I am wondering if maybe a water storage tank would be more appropriate for supplying water to both buildings.  from may discussions with my well guy, the main stress that any submersible well pump is the cycle of the pump turning on and off due to the demands of water usuage when there is not a storage installed.  The other is when, as previously stated, the check valve is not working correctly.  I have also been told that the proper placement for the check valve is at the well head, not above ground before the booster tank.  There should also be one after the booster tank .  You also have possible signs of a water logged booster tank/hole in the bladder, Just as WAYNEL5 stated. 

When using a storage tank, the well will turn on when the water gets to a certain level and shuts off when that level reaches a higher level within the tank.  Depending on how the float switch is set up, it could be a few feet, which could be a few hundred gallons per foot, depending on the size/diameter of the tank  On a system where the well head "creates the working pressure" for the booster tank, the cycle will become  more frequent as to the booster tank size and the min/max operating pressure.  This is sort of the same principle of a min/max settings on HVAC system.

In thinking about your situation, a double booster tank, one for each duelling, would be be better if the were run in a series(one connected to the other).  On the discharge end of the the booster tanks, the line would be tee'd to each duelling. My personal prefferenc would to have a seperate booster pump and tank that is feed from a single storage tank.  But this is probably the most expensive of all the scenarios, except for having 2 wells. 

There is also an issue of wire and breaker sizing that will be needed to be changed out if a booster pump is added to a system because now you would need to figure the amp draw if both the booster and well pump were to be running at the same time

From my memory, the water loses 1 pound of pressure for every 2 feet of rise.  So, a booster tank that has 50 lbs pressure and is 50 feet below your house, you would only have about 25lbs of working pressure in your home.(someone please correct me if this is wrong) The possiblity of putting the storage tank or even the booster tank up near the home might work depnding on the well pump size and it depth.  As an example, my well is 884 deep, well pump is set at about 770', ant the well pump is 2H.P. In my case the pump will loose it's efficieny if the booster tank is set near the home which is 30' higher.  So, in this case, a boster pump/storage tank is needed to get sufficient water pressure and volume up to my home.  My working water pressure at the house is 45lbs and the pressue at the booster tank below is at 60lbs

In reading your post a little more, I think that the two homes would still need to have their own booster tanks and each would need to be wired to a single magnetis swaith that would open when either one or both creates a demand.  You would still need to tee of from the main feed that comes from the well ant at that point, each indiviual line would need to have their own check valve after the tee.

I know that most of this is rambling, but I have been going for 20+ hours straight and maybe soon, I'll get some sleep.

And, another thing... All of the government required water saving/restricting devices that are now on all plumbing devices, they HATE lower water pressure.  I'd swear our Master Bath jacuzzi tub takes 15min to fill.  Who wants to wait that long, I know my DW doesn't and she is always reminding me to fix it.




(post #110358, reply #17 of 18)

Another 2 cents worth:

In the long run, it will save you $ to have a cistern that holds a large volume of water with a secondary pump (doesn't need to be submersible) that pressurizes a pressure tank.  The larger the pressure tank and the storage tank, the better.

The well pump can then be put on a timer switch (with a float switch in the cistern that overides the timer switch if the cistern is full) instead of a pressure switch.  This turn on the well pump less frequently and, as noted already, saves on the primary long-term cost of a private water system: submersible pump replacement.  The pump that pressurizes the house system is much less expensive to replace not only for parts, but especially since it is so easy to do without help or a cable rig. 

This type system also drastically lessens the problem of living on a low output well.  In the area in which I live, there are lots of people living on wells with output of 3/4 gallon per minute to 3 gallon per minute.  I've often heard warnings such as "don't buy anything with less well output than 5 gpm or 10 gpm, etc.  But wait!  One gpm is 1440 gallons per day!  Yikes! that makes 5 gpm more than 7,000 gallons a day!  The problem isn't source production, it's storage and delivery.  (I've lived a variety of, ahem, "non-traditional" water systems in a variety of very dry areas including one that had two homes on one well with a less than one gpm recovery rate and a 250 gallon storage tank.  Even with two kids in diapers we never ran out of water.)

All that said, a top notch rural system certainly isn't cheap!  But if you can swing the up-front cost, you'll be glad to have it this way.  Try big city salvage outfits for a good deal on a water tank.  Or go plastic, around here plastic tanks run about $1 per gallon.

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