The problem with using a 12v fresh water pump, is how the water box manual float and the demand pressure switch on the 12v pump work together. The water box float opens and closes to rapidly or the float flows water at a low gpm which is something these 12v pumps switches do not like, creating the 12v pump demand switch to overheat which temporarily makes the pump stop working till the switch cools off. Over heating this switch multiple times will destroy the demand switch eventually which is the problem. These pumps are designed to run approx. 3 gallon a minute or more like a house/rv faucet and the water box float limits this gpm, to less then half a gallon per minute at times which causes the demand pressure switch to over heat and stop working.
There are multiple ways to help with this. 1. Accumulator tanks, create passive pressure that is designed for this issue but not always perfect. 2. Or you can use a limited bypass hose to flow and circulate water back to you fresh water tank so the pump is always flowing water. 3. Or you can just run the 12v pump directly by bypassing the demand switch function. You can do this by changing 12v electric wires directly to the motor and always running the pump motor constantly which works good a long as a alternator is powering it. 4. Another thing that they do not make yet, that would allow the demand switch to work right, is a
differential float in the water box. A differential float closes when the tank is full but opens after the tank has emptied a certain amount or a bit lower then full. Not just on off rapidly like the floats they sell now and always have sold. Someone needs to make this differential float soon.
This picture is where they use differential float in large water tanks but they do not make it for smaller tanks like truckmounts have. Again someone should make and sell this.
Using a garden hose directly, you will not see these issue.
