Thursday, February 23, 2012

When A Well Pump Dies - Part 2

Sorry... just realized I never told people what happened with the pump.

About $1200 and several days later we had a working well again.  (Those of you who think that owning your own well is an inexpensive proposition should consider that number carefully before committing to it.  Well maintenance is not cheap.)

The best guess at the problem is that the slime (seen in the pictures from the earlier post) built up on the pump to the point that it loaded down the motor.   That might make more sense if you understand something about how at least some well pump controllers work:
  • A float switch in the tank indicates that the tank needs water.  (Our tanks are big - 5000 gallons each - and in theory it takes a bit of a drop before the float switch says the level is low.  In parts of the country with colder weather they don't use storage tanks, but they'd better have good wells that can keep up with demand in that case.)
  • The pump controller turns the pump on via a relay.
  • The pump controller monitors the current drawn by the pump, which starts at one value and changes substantially when the pump runs the well dry.  When that happens, the pump is no longer under load, the controller detects it, and turns it off.
  • Alternately, if you have a good well, the float switch hits the high water mark in the tank and the controller turns the pump off for that reason.
There are other complications, of course, like a timer to let the well recover before the pump is turned on again, but they don't really matter for the purposes of this discussion.

In our case it appears that the slime on the pump made it look as if it was under load - and moving water - even when it had pumped the well dry.  That meant the controller didn't turn the pump off, and since the water is the coolant for the pump, it wound up getting really hot and melting the pipe as previously documented.

The fix mostly involved cleaning the pump.  They bench tested it and found it was still OK, which is good and saved us a lot of money.  We also installed 40' of stainless steel pipe just above the pump to add more heat sink should this ever happen again.

I also get to put chlorine (in the form of bleach) down the well a couple of times a year now to kill off the bacterial slime that builds up and (hopefully) avoid this in the future that way too.

Such fun.  But we have a working well again, and the power bills are back to normal.  (Well, they were back to normal, but then a technician misread our old analog meter while installing a new smart meter, and I'm having PG&E look into that mess, but life moves on.)

May your water always flow.