Peggie:

I've got a SeaLand Tankwatch 4 monitor system for my holding tank. Lately,
the sending unit for the 1/2 full reading has become unreliable. When the
tank is half full, the gauge will read as such sometimes, but just as often
will not. When I know the tank is more than half full, I can rap on the top
of the Tankwatch cap with the handle of a screwdriver, and the 1/2 reading
will come to life.

The unit is acting as if either the float switch is being restricted from
its natural movement by grunge, or perhaps an unreliable electrical
connection. Due to other unrelated problems with the Tankwatch system, I've
had to replace the entire assembly twice in prior years. If it was an easy
job, I'd just remove the cap and examine and clean the reed switches to fix
this problem. The problem is that the manufacturer of my boat has buried
the holding tank in such a way that major surgery is required to access the
Tankwatch system. Having done it twice in the past, it's a several hour job
to gain access. A number of components have to be removed so the holding
tank can be moved to gain access. It's a big job.

I spoke this morning with Bill Friedman (great guy) at Dometic. He
suggested as a preliminary approach, to try and break up any debris that
might be restricting the movement of the float switch. He thinks there
might be dedicated chemicals to do such a thing, but couldn't recall any by
name. His recommendation was liquid laundry detergent. Fill the tank just
above half full, flush a small bottle of detergent into the tank, and let
things slosh around a while. Sounds like a reasonable approach to me,
rather than immediately committing myself to performing the surgery required
to gain access to the tank.

The boat is about six and a half years old, I've only used K.O. as a
treatment in the tank, and after pumping out the tank, I always fill it with
water half full and pump it again as a rinse. The head is a Vacu-Flush. Do
you have any thoughts to add or recommendations for an approach to this
issue?

Thanks,

Russ