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What height to get normal water pressure
By gizmo, Section Remote Living Posted on Wed Apr 14th, 2004 at 06:38:25 AM MST
What height do I need to get normal house water pressure from a tank.

Hi All
The place I'm renting has a large water tank out the back that I need to fill once a month from a bore. This is the main water supply for the house. There is a AC water pressure pump connected to supply the house water pressure. Problem is when the power goes out ( pretty common here ) I get no water!
I want to mount a smaller tank on a stand, and have a small windmill driven pump to trickle feed this "Top" tank from the main tank. An overflow on the top tank will run back into the main tank. This top tank needs to be high enough to provide normal water pressure to the house using gravity. This setup will mean I no longer need the AC pressure pump.
My question is how high will the tank need to be to get enough pressure. There would be a standard distance from the highest tap height to the top tanks bottom height to provide enough pressure for the highest tap ( in my case the shower ). Hope that made sense!
Anyone know the magic distance?
Glenn

What height to get normal water pressure | 8 comments (8 topical, 0 editorial)

Re: What height to get normal water pressure (none / 0) (#1)
by Gary D on Wed Apr 14th, 2004 at 07:18:09 AM MST
(User Info)

Biggest question if you know, what is the pressure tank set up for? Usually 20/40 lbs. or 30/60 lbs. Every foot of height equals I think .47 lbs. of pressure if memory serves me right. So if you do the math, a tank 50 ft higher than your highest draw would give you 23.5 lbs. of pressure without figuring friction losses. Will put you in the ballpark at least. Hope this helps. If you're situated on a hill, the tank can be at ground level higher on the hill (no tower). Gary D.

Re: What height to get normal water pressure (none / 0) (#2)
by River Goat on Wed Apr 14th, 2004 at 08:06:23 AM MST
(User Info)

Gizmo,
I have lived with several gravity feed water systems. The system here is a 1000 gal. tank on a hill about 60 ft. above the house. This supplies about 28 psi to the ground floor of the house; a little low but works good with standard equipment. I have used low pressure shower heads that work good with only 5 ft. of head (height from outlet to supply). If you can only get, say 20 ft. of head, you could replace the devices that need high pressure. Another alterative would be a battery powered pump, like the ones used in a RV, to supply pressure from the existing tank.

River Goat(Jerry)

Re: What height to get normal water pressure (none / 0) (#3)
by veewee77 on Wed Apr 14th, 2004 at 01:52:09 PM MST
(User Info)

If you are going to use solar and wind for electricity, I would do as Jerry said and use one of those RV water pumps. They will build your pressure to 40 pounds if you wan it that high and they only run when the pressure drops below a preset amount.
They run on 12V and you could actually use that to pressurize a tank and then it would run til the tank reached pressure but it wouldn't run again until it dropped below the preset lower pressure (usually about 30 pounds if memory serves me correctly).

This way, running water for a few seconds at a time won't make the pump cycle very often. Showering and other continuous uses would make it cycle more.

Doug

[ Parent ]

Re: What height to get normal water pressure (none / 0) (#4)
by pwmvsi on Wed Apr 14th, 2004 at 05:05:38 PM MST
(User Info)

There is a company in Denmark that builds a windmill well pump that are matched to each other. The companies name is grundfoss, I believe. Try google. And yes, it is .47 psi per verticle foot.

WS

[ Parent ]

Re: What height to get normal water pressure (none / 0) (#5)
by Nando (nando37-at-tx-dot-rr-dot-com Correct theanti-spam) on Wed Apr 14th, 2004 at 07:08:32 PM MST
(User Info)

First:

0.433 PSI per foot of height.

Why do you have to fill once a month, what about once every two days?.
How deep is the bore ( Well) ???.
You say you have the electricity, but goes dormant quite often -- please explain the once a month procedure.

For low pressure systems the house needs larger diameter pipes and larger shower heads .

Best way is to use a DC 12 volts pump for inside needs if you do not have at least 60 feet of equivalent pressure (26 PSI).
I have built systems that come on automatically when the pressure is reduced, also I have gotten a large tank,like 300 gallons filled about 50 % then air pressure to maintain the desire pressure ( the pump generates the air pressure by pumping additional water until the pressure sensor says stop -- like 100 PSI then start again at 45 PSI.

Regards

Nando

Re: What height to get normal water pressure (none / 0) (#6)
by Gary D on Thu Apr 15th, 2004 at 05:59:44 AM MST
(User Info)

I think you're right on the .433 per ft Nando. A search on Homepower puts it at 2.31 vertical ft. per 1 pound of pressure. So for 10 lbs., you'd need 23.1ft. vertically. 20 lbs., 46.2 ft. etc. Not counting friction losses. Not sure on the .47 no., think it was from a hydro ram websight, but I definately was wrong there. Gary D.

[ Parent ]

Re: What height to get normal water pressure (none / 0) (#7)
by Gary D on Fri Apr 16th, 2004 at 08:35:39 AM MST
(User Info)

Nando, in the few cases of a holding tank duel pump combo's I ran into over the years they were always for low yield wells. The deep well pump was on a timer to turn on for a set ammount of time per hour depending on the sustainable recharge of the well. No safety's installed to keep that pump from running dry (if the well yield dropped). The shallow well pump was usually a jet type for pressure into the house. If you used more water than the well produced, you would need to have city water brought out to fill your"holding tank". The mistakes I usually ran into were burned out deep well pumps due to running dry and overheating. These were homes built before the wells were ever drilled. Since that time, most areas now require wells to be drilled first (good thing). Don't know if this is gismo's case tho, due to the statement of filling out of the borehole once a month. Gary D.

[ Parent ]

Re: What height to get normal water pressure (none / 0) (#8)
by Kingscoop on Tue Apr 20th, 2004 at 06:20:49 AM MST
(User Info)

Why all the maths? To work out the head at any tap just connect a hose and turn the tap on. Lift the free end of the hose until the water stops coming out. Measure from this level down to your tap and that is the water head. (Or am I missing something?).

What height to get normal water pressure | 8 comments (8 topical, 0 editorial)

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