grinder pumps

Status
Not open for further replies.
augie47

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
I work an area where sewage grinder pumps are prevelant. Most times, individual residential units, sometimes, a field of 10-20 for a sub-division.
Some have engineered drawings, most don't.
In an area coverd by 10 or so different inspection agencies, the installations vary from PVC with no sealing whatsoever to GRS with explosive seals-offs.
Is there any "standard", or does this vary too much from unit to unit?
 
Installations at dwellings typically will not be classified, however this is left to the AHJ to make that call. At the least, duct seal or some other approved material is needed to reduce/restrict the transfer of corrosive gases from the wet well into the controller enclosure, however classifying that gas as a hazardous substance may be a stretch.
 
Believe it or not in our area there were many septic pumps (not grinder pumps) that were installed with the electrical outlet inside the tank. Boy, what a mistake that was, however I have never heard of any septic tanks exploding just a lot of corrosion on the receptacles. Now we have an exterior box with an alarm that must be feed by 2 circuits (one for the pump and one for the alarm) and both ends of the 2"PVC, which encases the cords from the tank must be sealed with duct tape (edited to duct seal) Also the hove into the tank (usually concrete tank) must be sealed with hydraulic cement.
 
Last edited:
I did a few commercial systems where the inground (400 gallon vented fiberglass) tank had 2 pumps and the level control floats inside.
The conduit connection for the tank JB was underground and 2" pvc was run from that point to near the (remote, wall mounted) control panel.
At that point, the underground PVC conduit was changed to 2" rigid steel from the sweep elbow up to the control panel.
In this short section of 2" rigid, I was required to install a seal fitting.
There were approx. 20 conductors installed in this conduit (control and pump leads).
I believe that he (the inspector) classified this as a Class 1/Division 1 location.
I knew ahead of time (from another sparky) that the inspector was requiring this, so I was prepared.
At the time, I didn't contest his logic or reasoning because it would have been fruitless, I just complied and got it passed.


On the residential systems that I installed, the factory supplied cables were rated for direct burial, so the solution was to only use conduit at each end where the cable emerged from the ground and leave the cable exposed underground.
Basically disconnecting the path (two conduits from each other).
Luckily, he wasn't worried about gas migration inside the cable sheath.
In my opinion, these are not Classified installations, but we know about opinions and everyone having one of their own.
The tanks (and control panels) are vented to atmosphere, and are being pumped down several times a day.....Too much dilution and not enough time for any serious "fermentation" (gas generation) to take place.
It's a good thing that we didn't have any electric lights on our "out house" when I was a kid.
They wouldn't have passed "inspection", and I might have been blown sky high.
Just some thoughts and opinions.
steve
 
Status
Not open for further replies.
Top