David, I have the same model with no problems. I was living in my westy for
about four months with this model and never had any problems. It is easy to
see when it is full or about too. The holding tank doesn't hold that much
(same as fresh water tank) but the size makes it very convenient. My kids
use it as a step to get into the penthouse (upper bunk). I stand on it.
Pretty durable outfit.

Bill  V.                 "I'd Rather Be Hiking The
'82 CA Westy [FreeBird]       Greater Yellowstone"
"Famous Potatoes"

>
> At 12:34 12/10/99 , Bulley wrote:
> >Boy, not sure which Thetford you have there, but that's not a problem on
> >ours at all...
>
> The baby, model 135.
>
>
> >Also, there is no "vent" on ours. When the waste-entry gate is closed,
> >(with a completely full tank or not) you can shake, tumble, and roll the
> >container, and it doesn't spill a drop.
>
> Right.  But when you build up a head of water in the bowl and
> then open the
> flush gate, it will drive (treated) sewage through the sliding air
> vent  that's part of the gate mechanism, until the levels equalize.  I've
> never experienced this -- _Practical Sailor_ downgraded the Thetfords when
> they looked at chemical toilets because of this "feature."  Other
> than that
> they liked them.
>
> david
>
>
> David Beierl - Providence, RI
>   http://pws.prserv.net/synergy/Vanagon/
> '84 Westy "Dutiful Passage"
> '85 GL "Poor Relation"
>