They used to drill holes just above the low water mark to take the head
pressure off the pump as the didn't put the check valve down low like moden
installers do now. What used to happen is the pump would run and nothing
would happen for a bit until it had the head pressure built up then it would
pump. I don't think the old pumps were built as nice or have the head
pressure of a modern pump.

Rich



Pop` wrote:
Sudy Nim wrote:
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

The check valve is located as close to the pump as is practical. I
have NO idea what the other poster is talking about w/r to not on the
pump, and -drilling- an airhole. It makes no sense, and drilling airholes
is silly as there IS no air to create a suction in a properly
installed sump pump system; it's not a closed system.
My current sump came with the valve pre-screwed into the pedestal,
ready for th PVC to connect to it. ANY instructions I've seen on the
check valves I've had to purchase ALWAYS have shown the check valve
screwed into the sump pump via the threads provided for it.

In general, the check valve should be close to the pump so that there
is less air to trap in the pipes between the pump and the valve;
gives it a faster startup and the water standing in the pipe won't
compress and cause "spurts" when the pump comes on.

I can see zero advantage to two check valves unless you're just
thinking of redundancy. However, each chack valve does offer a
finite resistance to the flow of water, so there would be some
slowing of the water movement; no idea how much. It IS a good idea
to have one on hand though, just in case it's needed. They're very
easy to replace. So I don't suppose it'd hurt a LOT, especially if
the water didn't have to pump upwards very far, but ... I really see
little benefit. I seem to get about ten years out of a sump pump,
and have never yet had a check valve go bad on me.
http://en.wikipedia.org/wiki/Sump_pump
and also:
http://en.wikipedia.org/wiki/Check_valve

HTH
Pop`