I am not sure I am doing the filling with blue correctly and can't seem to find instructions giving the amount of water I need to put into the holding tank. When changing I am adding approx 30ml of blue (as per instructions) and then approx 6 litres of water in the holding tank. Am I doing this correctly as it seems to be quiet a lot of water when it takes the flushing water and the usual little wee's.

To be honest, Taffy, I always use the blue sachets the container of which takes up far less room/weight when travelling. I usually drop 1 sachet into the Thetford tank and add approximately 1 - 1.5 litres of water. It's not an exact science hence the approx figure and I just tip enough fresh water into the tank until I think to myself 'that'll do'.

Thanks Deeps for the reply, as to my mind to add 5-6 litres of water seems a little excessive for preparation and before use and the flush water is added. I will add less the next time. I do the same with the flush water and add what I think is just about right as I use the thetford spray in the bowl which does work very well.

We only have a Porta Potti. I dribble a very small amount of the blue and then a few drops of water and that's enough. It works well as far as we can see and smell

Because we emptied ours everyday we just used cheap stuff from Tesco wherever, no smells except pine needles (which was the smell of the one we chose)

The instructions on mine state add 5 litres, but I think Aaron is correct that this is to cover solid deposits. I use a bit less concentrate and 1 litre of water and the wash room always smells fresh.