A pump doesn't really suck. It just reduces the atmospheric pressure
at the inlet. The lack of atmospheric pressure at the inlet will push
water into the inlet. Atmospheric pressure is about 14.7 pounds per
With the maximum 14.7 pounds to work with the practical maximum for
the best of pumps is about 25 feet. This 25 foot design would not be
easy to prime, and would not be easy on the impeller long term.
You would be better served with a submersible or some sort of jet
Need review of what horsepower does on pumps.
I have a well, 29' below where the pump will be. It now has a 2hp Sta-Rite
pump on it.
I'd like to put a 1.5hp Sta-Rite on it, because of economics.
Does the HP of the pump relate to how much suction it has, or does it relate
to the number of sprinkler heads I feed with it?
If it relates to number of heads I feed with it, I know I can get by with a
smaller number of pump HP. I have 3 sections of 4 heads ea.
The answer is all of the above, plus other factors like how long the
pipe runs are, how large diameter pipe, how many GPM the heads are,
what flow rate the well can support, etc. I can tell you this. I
recently had a 1hp submersible installed on a 50ft well. The water
depth is about 40ft below ground level. It serves a 10 zone system,
where the largest zone has 10 heads doing 15GPM.
Summarizing everything that's been said, you can't tell from what you've
presented. For example, what is the flow rating of the heads you are using?
Do you plan on expanding the system in the future? Does your system use a
pressure tank, (high pressure, low volume pump), or no pressure tank (high
volume, low pressure, continuous run pump)? From your description it may
even be that the smaller pump is preferable, if the larger one is oversize
for the application -- more likely to heat up because there isn't enough
water being pumped.
We recently had to fix a system that had a mismatch between pump size and
application - the original DIY'er had put in a large pump (future planning)
but a small pressure tank. Worse, the pump was high volume, low pressure,
not matched to the pressure tank. If you could stop the pressure switch
from chattering, it would fill the tank in seconds, then shut down while the
tank bled down during irrigation, but restarting after only a minute or two
of operation. We fixed it by replacing the original pump with a high
pressure low volume pump and replacing the small pressure tank with a 100
gallon hydro-tank. Now the pump runs for 3-4 minutes, then shuts down for
about half an hour. We also could have removed the pressure tank and
operated the irrigation system directly from the original pump, but there
was an outdoor sink at the green house that we didn't want to have to
In your case, I'd take the information on my system to a local irrigation
systems supplier and get their advice. You'll probably find that they can
steer you in the right direction, avoid buying the wrong items - and that
their products are as inexpensive and probably better quality than what's
available at the box stores.