Well Question

[spamtrap100]

Am building a house that shares a well with two other lots. The shared well is located approximately 350-450 feet from the three building sites. The original plan was to run a separate supply line from the boost pump/tank located near the well to each house. Due to a screwup by the now ex site supervisor, only a single 2" line was run under the road before the trench was filled and the road paved.

The owners told the developer that a single 2" line would not be able to supply pressurized water to three houses. Wishing to avoid digging up the road, the developer was able to run a second 1 1/2" line through the conduit, but there was not enough room to run three separate lines as originally planned.

There were two options for managing the water lines after the run under the road (you'll need to view this message in a fixed font to get the picture):

Option A

|P| | |---------150'-----1 1/2"--| | |u|===| | | |---300'---------House 1 |m| | |=========150'=====2"======| |---200'---------House 2 |p| | | | |---200'---------House 3

Option B

|P| | |---------150'-----1 1/2"--------300'---------House 1 |u|===| | | | |m| | |=========150'=====2"======| |---200'---------House 2 |p| | |

Option A was to use a manifold that combined both supply lines after the road, then split off three house supplies from that manifold. Option B used the smaller supply line to supply the house farthest from the well exclusively, and then a splitter off the larger line to supply the two closer houses.

We ended up going with Option B, but I really can't see that either option was preferred, given that there is a single boost pump supplying both lines and the fitting on the pump is smaller than the larger line.

Thoughts?

[dpb]

A chain is no stronger than it's weakest link. Similarly, the minimum single point restriction is the limiting factor here.

I predict this will be unsatisfactory in the long run as depending on usage, somebody will be low on flow/pressure.

The answer should have been "none of the above" and the trouble to run a larger line to a sizable storage/booster tank run. Failing that, one could get by by rejoining the two feeders into a common header and using that to feed a communal larger supply reservoir so the upstream pump limitation is compensated by a larger reservoir.

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[Art]

Why can't he run another pipe under the road. Utilities do it all the time without damaging the road.

[nicksanspam]

With option C:

Houses 2 and 3 can get more water from the 1.5" line if House 1 isn't using any water...

Nick

[EXT]

Local gas utilities and water departments run either plastic lines or copper lines with either a horizontal drill or an air powered torpedo that will run under the road without digging, even where there is no road it is cheaper to use than to dig up the whole line.

[Rick Blaine]

Don't know for sure - that was my first thought as well. The road is cut into a rock mountain, so they would have had to dig up the original trench to avoid cutting more rock, but that shouldn't be that big a deal.

-- "Tell me what I should do, Annie." "Stay. Here. Forever." - Life On Mars

[Rick Blaine]

Unfortunately, this road is cut into a granite mountain side, so that type of installation isn't an option.

-- "Tell me what I should do, Annie." "Stay. Here. Forever." - Life On Mars

[Rick Blaine]

Hmmm... Not sure I follow your drawing. It seems to be missing house 3.

-- "Tell me what I should do, Annie." "Stay. Here. Forever." - Life On Mars

[Rick Blaine]

Well, then it shouldn't matter. :) There is a couple of hundred feet of lift involved in addition to the run length, so it will be interesting to see if the boost pump is sized properly.

-- "Tell me what I should do, Annie." "Stay. Here. Forever." - Life On Mars

[David Martel]

Houses are expensive. A civil engineer can answer this question. The developer needs to hire an engineer or dig up the road. Digging up the paved road to install new pipe is a common occurrence and not a huge expense. If the developer tries to put a "band-aid" on this problem you need to get out now.

Dave M.

[M Q]

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I assume that you meant to also include house 3 on option B. No one seemed to ask:

1) what is the expected flow rate of the pump? (at the anticipated pressure) 2) are the houses at the same elevation? If not, you are going to have far more problem from that than from any slightly undersized pipe. 3) What do you expect the demand from the houses to be? 4) Is the entire 150' distance under the road. If not, you could replace/augment the portion that is not under the road.

The combination of a 1.5" and a 2" pipe as in option A is equivalent to just slightly under a 1.5" pipe for each house. That is probably more than enough for most domestic uses unless you have fire sprinklers or plan to do high volume outdoor irrigation.

If the houses are not at the same elevation, you may want to consider either pressure regulators, or secondary pumps and/or tanks at the houses.

P.S. My preference would be option A. Unless all three houses are simultaneously using large volumes of water, it will give superior performance.

[Rick Blaine]

Whoops. Yep - you are correct.

That I will have to see next time I climb down into the well house. That's really the key question.

Yes, they are all approximately the same elevation.

There's little to no outdoor irrigation allowed, so it's household use only. Worse case would be less than 10gpm per house I should think. The houses do have active fire supression (sprinklers), though one wouldn't suspect more than one house would be using them at a time. :)

The road is only 30' across. The developer and his well company were OK with the single line servering 3 houses and someone else here suggested that 5 could be served off a 2" line if the pump would support it.

We'll do some performance testing before accepting the house. It may be years before the other two houses get built and we can deal with any problems then.

-- "Tell me what I should do, Annie." "Stay. Here. Forever." - Life On Mars

[Edwin Pawlowski]

Only one thought. You need an engineer to do the calculations to see exactly what you need. IMO, you have plenty of capacity to supply another three houses too. Be sure you have the right pump setup. It is far cheaper to pay an engineer a few hundred bucks now rather than have to re-do a faulty system a few months from now.

[Rick Blaine]

In this particular application there is no pressure tank. The well pump fills a

1500 gallon storage tank and is controlled by a float valve. A booster pump draws water from the storage tank and supplies water directly to the houses.

It would be hard to imagine the houses drawing more than 30gpm combined at any one time and that number seems well within the capacity of a boost pump.

-- "Tell me what I should do, Annie." "Stay. Here. Forever." - Life On Mars

[Bob F]

Except for the digging up the road part.

[Bob F]

My hose faucet running full blast puts out about 15 gal/minute.

No pressure tank? Does the pump run full time?

Connecting the 2 pipes together before splitting to go 3 ways would help assure that noone gets short-changed on water.

If there is a problem, increasing the pump pressure should solve it. (Bigger pump) I wouldn't expect it. Without watering usage, high demands should be short lived. A pressure tank at your house could solve that.

Bob

[Rick Blaine]

Well, the houses will have outdoor taps, but are prohibited from doing any irrigation. I suppose washing a vehicle could draw the amount you indicated.

When water is being demanded, yes. Thought that was a little unusual but the other houses in the development use the same arrangement with no problems.

That was my first reaction, but now I'm not so sure. :)

That's my backup plan if there's an issue. I'll just put a 1500 gal storage tank near the house and draw from that.

-- "Tell me what I should do, Annie." "Stay. Here. Forever." - Life On Mars

[M Q]

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With sprinklers (I assume required by building code), the fire codes and local fire authorities are going to tell you what size pipe you need, what flow rate, and whether you need to sustain that rate for just one or all three houses.

[Rick Blaine]

That was my thought also. I can't recall what the rule was right now, but I know the code inspectors are pretty strict around here.

-- "Tell me what I should do, Annie." "Stay. Here. Forever." - Life On Mars

[dpb]

"...given that there is a single boost[er] pump supplying both lines and the fitting on the pump is smaller than the larger line."

If I interpret this correctly, the system still has a single-point choke point. Downstream of that increasing the line size or number of lines can't help w/ what is an upstream restriction. Am I wrong?

The tank at the service end resolves the problem in that manner as long as the total demand isn't greater than the tank capacity. Only place that should be a problem would be perhaps in the event of the sprinklers being in play, I would think.

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