caravan water tank - HELP

i've got the little plastic hose clip things on the 12mm hoses and a stainless steel hoseclamp on the filler.
i could maybe tighten the hoseclamp a bit more but its only a fairly fragile plastic fitting to if i go too hard on the hose clamp i'll break the fitting and then im in all sorts of trouble.

cheers,

KG

Plastic hose clips are not worth a pinch of poo.
If you are using the correct type of hose they are nearly self sealing on those poly tanks. What type of hose are you using?

"The manufacturers of my campoer put a tap my camper put a stop tap on the hose that leads to the pump. They said that you should turn the tap off when filling to avoid water running out the spout and flooding the trailer."
That was only because the dummies could not design a proper system.

That white covered food grade hose is not at all suitable for direct connecting to the inlet of a poly caravan tank. I was under the impression you wanted to use the thread tape because one of the threads was leaking.
On the fill hose use a piece of soft clear good grade hose, which should be such a snug fit the hose clamp only needs to be done up a little.
The white covered food grade hose can then be connected with a cheap poly line connector you buy at an irrigation shop to the clear poly hose. Leave about 150mm of the clear hose before connecting the white hose. The only way you can use that white covered food grade hose is if there is no movement of the tank or hose at any time. You used to be able to buy the soft food grade hose in black, but it is no longer available, so what you will need to do is put black insulation tape over the clear hose to keep the light out as that is what causes contamination of the water.
You can get a cheap breather tap from the garden irrigation shops for $2.50 or thereabouts.

One of the ideal breathers if you only need it for taking water from the tank, is a small duckbill rubber breather used in chainsaw fuel tanks.
That type of breather only requires a small hole of 3mm and can be placed in the breather pipe or anywhere convenient including directly into the poly tank. I purchased one from a Homelite chainsaw dealer for $2.85.