Re: Gravity feed vs pump question

[humbug]

Good question Deb. I have trying to find information on pretty much the same thing. How many foot of fall per pound of pressure? I hope someone can help us out.

[fredfl]

Pressure is not a function of quantity of water it depends upon the head i.e. how much higher the water outlet is than the area you want to irrigate. I used a gravity feed irrigation system at my last home that was fed from a brook which was about 15 feet above my garden and I would guess I had about 10-15 psi which was fine for general watering. If you don't have any area on your property which is at least 10 feet higher than the area you want to irrigate you will probably have to use a pump. There is a large amount of pressure loss in a garden hose vs 1" black pipe due to friction, I used to run black hose from the brook to the edge of the garden and then about 50 ft of garden hose to minimize friction losses.

[kawalekm]

Hi Deberosa
Figure on about 0.5 PSI for every foot of altitude above your sprinkler head. *A pool 3 vertical feet above where you want to water is only going to produce 1.5 PSI. *Most drip systems are designed to work with pressure no more than 25 PSI, so that is equivent to about 50 vertical feet of drop. *Friction from pipe size is important, but more so for long runs more than 100feet. *With 1" pipe PVC the pressure drop per 100 feet is less than 1PSI. *You can go to the Torro and Rainbird websites to get exact data on pressure loss.

With pressures that low, I'm not sure if most drip emmiters will even work properly. However, since you can run hose directly from the house, could you also run hard pipe? How is the house water pressurized. Do you have a pressure tank, or is it on-demand from the well pump. At our homestead, we have 5000 gallon tanks about 200 vertical feet above the well. For everything except watering the whole orchard, we have too much water pressure!
Michael

[huckelberry]

if i remember correctly...1.5 psi per ft of drop per cubic inch of volume,that should let you figure pressure at any elavation...huck