Flush tank additives

We had caravans for well over twenty years. Originally we had a removable Porta Potty toilet, as did many others... The last three caravans had a fitted Thetford toilet, with a separate flush tank to which I always added pink fluid. Rarely did I see black bits in the flush water, but then I have always fully drained the flush tank and indeed all the water systems between trips.

For over three years we have had a motor-home, it too has a fitted Thetford toilet, but it has NO separate flush tank, the toilet flush comes from the underfloor tank just like the taps so adding anything to it is not an option. Even so, I rarely see any black bits in the flush water, and as before I fully drain down everything between trips.

I have a theory therefore, that the presence of black bits or not in flush water, has less to do with what you add to the flush tank, and perhaps more to do whether the water in the flush tank is left in between trips, either fully or partially, and that its actually the damp conditions in the flush system that is causing the black mould which you see, similar to what you see in washing machine detergent drawers, which the OH has also started removing to dry out between washes.

. . . . though what goes into it is the same.

I've mentioned this on a previous thread on this subject but just a word of warning about warranty on the flushing pump which can become clogged if too much softener is used. Probably wiser to use the "pink" stuff if your van is still under guarantee. 

I'll never go back to using the pink stuff.  My flush tank is now filled with clean water only and I spray the toilet bowl with a fragrant but diluted disinfectant to sanitise the bowl.

We have tried both fabric softener and disinfection in the top tank.

Didn't like the fabric softener as it left white slimy film on the mechanism, the disinfection was ok to start with but then we found when staying put for a few days (MH then) it would settle in the tank and the mix wasn't consistent.

We have now gone back to a 'little' bit of pink in the top tank and a good squirt of disinfection mix every one in a while.

I have a theory therefore, that the presence of black bits or not in flush water, has less to do with what you add to the flush tank, and perhaps more to do whether the water in the flush tank is left in between trips, either fully or partially, and that its actually the damp conditions in the flush system that is causing the black mould which you see, similar to what you see in washing machine detergent drawers, which the OH has also started removing to dry out between washes.

I am with Jill. I stopped using the pink because of black bits. Only used plain water for the last 7 or 8 years .... maybe longer. Don't drain between trips and no black bits. 

for what it's worth, a few years ago I mixed the pink in an old 5ltr water bottle to save time when topping up through the holiday. At the end of the week I had a couple of pints left which I decided to keep til next time (call me Scrooge) but when I went back to it about 6 months later the bottle was full of little black bits. It was a clean bottle to begin with and I used fresh clean water, so can only conclude that this has something to do with the breakdown of the pink stuff and nothing to do with seals or pipes in the flushing system

Didn't like the fabric softener as it left white slimy film on the mechanism

does not look or feel great but keeps the rubber seal flexible and helps stop corroision, wipes off easily with a wet wipe.

Does it really matter if you get black bits in the flush water? It ends up in a toilet cassette! 😉

Used to use Pink in the flush tank, just lately started using supermarket own label disinfectant (roughly 25pence a litre)