"Paul Hovnanian P.E." <paul@xxxxxxxxxxxxx> wrote:
> Another thing that works well (if the OP has the room for it in his
> tank) is a float switch. There is a type which is a tilt switch
> encased in a float that hangs from its cable. The float is buoyant
> cable end down, so when the fluid reaches it, it tips to one side,
> closing the circuit.
> These are used in pumped sewage systems, which are even more
> contaminated than most washing machines.
Don't most sump pumps come with one already installed? They are a bit of a
pain to adjust, and I have had problems with reliability. Either not
shutting off, or failing to turn on. Sometimes the switch breaks or jams.
Sometimes the float sinks. I think these are fine for sewage plants, where
someone is constantly available to maintain them. But I have a suspicion
the diaphram may be much more reliable.
Of course, you really need two. One to trun the pump off when the level
falls below the setting, the other to turn the pump on whe the level rises.
Now comes the tricky part. It needs some form of memory to realize that it
has turned on because the water level rose, but it shouldn't run off until
it clears the lower sensor. This could be a simple relay, but now we are
adding complexity and more failure modes.
So perhaps there is a simpler method, for example using fluid logic, that
might be more reliable?