I am looking for a device that can be attachd to a hose that will measure the amount of water going into my tank so that I can partial fill before my trip and then top up just before camp, thereby not having to carry hundreds of litres unecessarily. There has gotto be an easier method than timing the fill of a 5 litre bucket. Thanks
Use clear hose on your feed hose to your pump (If you can see your tank and it picks up from the bottom of the tank) and just shut the water off when it's at your the amount your after.
We used that system on caravans for years and other than having to get down and look under it, it can't fail.
If you wanted to go high tech you could fit a fuel tank sender in the tank and a gauge near the fill point.
Good flow meters are expensive, cheaper ones from Bunnings will give you a general idea though but wont tell you how much is actually in your tank.