What sort of electric water pump is suitable to power a residential
sprinkler system fed from rain-water storage barrels?
I've got about 340 gallons of rain-water storage contained in a handful
of food-grade plastic barrels that I want to manifold together to feed
an electric water pump that can be connected to a 1 or 2 head sprinkler
system in place of municipal water supply.
I don't want to spend a fortune on a pump, ideally $100 or less. The
pump would have to be a non-submersible type (I don't want to put it in
any of the barrels). This rules out a lot of sump and sewage-type
Running dry will fry the pump quick enough but so will turning off the
water flow and leaving the pump running for an extended time. A few
years ago my neighbor asked me to turn on my pump so she could water
her garden. I turned it on for her but had to leave for a few hours. I
left her with very explicit instructions to unplug the pump when she
was finished watering. I even took her down to the river and showed
her the pump and plug.
Big mistake, that's all I can say. She shut off the water and left the
pump running. When I got home I could here the pump screaming two
hundred feet away.
The pump is only used when I want irrigation water it's not on a
pressure system. I only used to use it a few times a year. A pressure
switch is a good idea. I have recently remarried, my wife is planting
flowers all over the place. She's bound to do the same.
I don't think I would bother with a pressure switch or a pressure
tank. Design the distribution systems so they flow about the same
rate. Then select a pump that is just over that flow rate and just
turn it on when the valve to a zone is turned on. A pressure switch
will simply end up cycling the pump and that's worse for it that
making it work a little harder.
What is definitely needed is an out of water switch that prevents the
system from running when the tanks are empty.
You could do all of it with a basic irrigation timer that has
provisions for a pump turn on and a rain shutoff. Many do. Just
arrange your out of water switch so it behaves like a rain turn off.
She probably nodded and said she understood what you told her but didn't
have the first clue as to what you were talking about. If you later
didn't allow her the use of your pump, she probably thought you were
being mean and selfish. :-)
I pull water from my pond for irrigation. I use one of the harbor
freight pumps that has a small built-in pressure tank. You would run
combined outlets of your tanks to the pump inlet, run the outlet to a
water filter(the regular household type with replaceable cartridges)
and the outlet of the filter to your sprinkler heads. Setup works
well for me. If you don't use a filter, the sprinkler heads will clog
unless your water is really clean.
As othes have said, you need a float switch to prevent pump running
dry or you will wreck your pump. Total flow will be set by the
sprinkler heads you choose, but 340 gallons isn't that much.
You may want to consider a drip system. The come with tiny pumps and
make much more efficient use of water. Google drip irrigation system.
You can get complete kits with everything you need for not much $$.
Some sump pumps don't develop much pressure. You need some pressure
to operate sprinkler heads, at least 50 - 60 psi. Drip normally uses
25psi so it is an easier solution. I agree with the others that's not
much water. A single sprinkler head can use 5 gal per minute.
I fix pivot irrigation systems. Nelson makes sprinkler heads that
will work on as low as 10 psi. The ones in my area are typically set up
to operate on 20 psi.
It looks like 340 gallons would put 1" on about 540 sq. ft. if my
figures are right.
Guys - this is not some large farm that I'm trying to irrigate.
It's a heavily tree-covered urban front and back yard - about .3 acre
I plan to add more rain barrels over the next 6 to 12 months. Because
of a very wet and cold spring and early summer, I haven't had to use
much of this water yet to do hand-watering of various potted plants,
flower beds, etc. These barrels were full by early April - mostly from
melt water from last winter's snow. I probably wouldn't apply more than
1/3 inch at a time anyways, which would cover about 200 square yards by
my calculations (assuming 375 gallons of stored water - a little higher
than I claimed earlier).
You should still include a mechanism to detect an out of water
condition. The main problem with stored rain water for irrigation is
that you run out of water. If it doesn't rain for an extended period
that is when you will place the highest demand on your supply. You
alos might want to look at other storage tanks. You can get some big
plastic water tanks off craigs list pretty cheap if you have a rural
community nearby. Farmers use tanks that hold several hundred gallons
Not generally feasable in a regular community. Even to get 10psi
requires over 20 ft of drop. About all you can do without a tower is
let the water run out the end of a hose. Forget running sprinklers.
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