Ed Humphries wrote:
My sailboat does not have a head, but our motorhome has a holding tank
that can get bad - at least it was when we got it; we try to take
better care of it than the previous owner.

Perhaps Peggy will have some idea of how/if the following might help
with a marine head holding tank.

At the beginning of a trip (where we knew we could dump at the
destination) we put a bag of crushed ice (plus all the cubes we had in
the freezer) plus a bunch of water down the toilet. The ice sloshed
about nicely as it slowly melted and scrubbed the tank. We dumped,
rinsed, and all was well with the tank (as far as I can tell!).

Prior to our doing that the tank was slow to drain and rinsing was a
waste of time. We used fresh bacterial starter after the "deep
cleaning" (don't know if Peggy approves of that or not). Now-a-days
everything seems to dump as nice as can be (given the subject matter
:-).

Sounds like a plan to me. And I very definitely approve of your use
of a "bacterial starter" instead of toxic chemicals. In fact, the
bacteria prob'ly did as much to open your drains--by digesting and
liquifying the waste--as the ice did. However, I doubt that the crushed
ice remained ice long enough to do much scrubbing...though it chilled
the tank enough to make the ice cubes last longer...it was the ice cubes
banging against the walls that accomplished that.

--
Peggie
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Peggie Hall
Specializing in marine sanitation since 1987
Author "Get Rid of Boat Odors - A Guide To Marine Sanitation Systems and
Other Sources of Aggravation and Odor"
http://69.20.93.241/store/customer/p...40&cat=&page=1
http://shop.sailboatowners.com/detai...=400&group=327