Is it better to have the check valve located at the base of the pump
near the inlet or further away on the discharge pipe above the pump?
Also, would two check valves be of advantage, one at the base another
a couple of feet above the base? TIA
One valve up, outside of the pit, is what you want. ANd don't forget
to drill a small air relief hole drilled in the discharge pipe an inch
above the pump angled down int othe pit. This prevents airlock.
You don't want the checkvalve screwing right into the pump. I recall
reading that explicitly in instructions, though I have to confess i'm
not entirely sure why. It may be that it prevents the inclusion of an
air relief hole, dunno.
I have found little need for a check valve. I live in an area that freezes
in winter. If you install a check valve it will hold water in the pipe
allowing it to freeze and then the pump cannot remove any water.
When I originally installed it without the check valve, I found that the
discharge end would end up submerged in the ditch and would siphon water
back into the sump causing it to cycle on/off every couple of minutes. I had
to break the siphon.
I decided that it was necessary to introduce air in the line to break the
siphon and to allow the 90 foot run to the ditch to drain. At the time they
didn't sell those devices for use in drains without a vent, but I had a
spare foot valve for a well pump, I cut a tee into the discharge pipe added
an 18 inch riser and installed the foot valve. When the pump pumps out the
foot valve is closed so no water leaks out, but as soon at the pump turns
off the weight of the water creates a vacuum which opens the foot valve and
lets in air that drains the pipes back to the pump and to the ditch. This
same foot valve has been in use with no problems since 1970. The only
disadvantage is when the valve opens it makes sounds like an old man with
bad gas, which isn't that bad, because when I hear the sound, I know it is
That's why you put the check valve indoors, and angle the pipe downward so it
will drain. I, too, live in an area that freezes in winter -- and I've
*never* had that problem. Your problem was caused by poor drainage of the
discharge line, not by the check valve.
That's why you use a check valve: so you don't siphon the ditch into your sump
Doug Miller (alphageek at milmac dot com)
Yup. Mine is above the pump, above the top of the sump, but quite
If you have a redundant pump system like a basement watchdog it should
have its own checkvalve separate from the main pump, and the Y to the
discharge heading outside should be above or downstream of both check
Yes, it probably was because the 1 1/2" poly line was not perfectly flat as
it traveled 90 feet to the ditch. This is what happens when the final grade
was done 4 months later by a bulldozer and compressed the soil. However, I
have found that eliminating the check valve has eliminated any problems that
could be caused by using it: frozen discharge line and the check valve
sticking open. Using an air inlet valve was a simple and workable solution
for the past 36 years.
2 wrongs don't make a right.
But 3 "lefts" do.
I'd count yourself a lot luckier than smart about using a discharge
without positive slope and making it work by eliminating a check
If you did put the check valve on the suction side of the pump it would
have the same effect as the foot valve on a portable pumps drafting
hose. When a portable pump must pump against a high discharge pressure
it must also have a discharge side check valve and a pressure release
valve upstream of that check valve to allow the pump to start without
trying to start against the back pressure of the standing water already
in the discharge line. Submersible pumps such as sump pumps do not need
an intake check valve and if one is installed it will cause excessive
ware on the pump's motor by causing it to start under load.
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