Toilet filling

A bit more info may help with a solution what holding tank?

Presumably the flush tank?

free2419.......generally the removable cassette tank is called the "holding tank", but pretty sure you are talking about filling the flush tank?

And there are different types of flush tanks. Some incorporated in the body of the toilet with integrated filling tubes and some with external filling points. 

If it’s an exterior filling point, it is difficult to envisage what would be blocking it. If it’s the older hand pump type flush, rather than the electric pump, all that unit can be removed and gives you good access inside the tank to see what is going on. I had to replace one on our old Abbey when it broke. You will need some sealer when you replace it though. Sorry no idea about the electric variety, as the one on our Bailey was still working when we sold it.

If your toilet is like ours, Free, the filler always holds water giving the appearance of being full (pic4) but it will still allow you to pour more in. The glass level indicator tube can be seen in pic1.

Thank you all for your reply I will try again 

Could anyone help with the amount of toilet fluid you need? The manufacturer of the fluid says 50ml/ litre for the flush and 65ml/ litre for the lower tank. What I do not know is how much each tank holds. I cannot drain the flush tank without continually flushing as there is no drain pipe. Also I do not know how much water to add to the lower tank initially. My reason for asking is because I am trying out "green" fluids whereas previously I have used blue capsules and rather hit and miss with the pink. I am trying to make up a measure "bottle" for each as my waste tank does not have a measuring cap. My caravan is a Lunar Clubman CK. Hope you can help me get to the bottom of this? Oops

 CHEEKY  !! 

Have checked the caravans manual but it just says " The amount of fluid required varies with the Tank size" but no mention of the capacity of each type. What a bummer!

I think you might get the size of tanks from the Website of the manufacturer {of the toilet }

 Mr Google should be of assistance, he is usually