Thank you everyone for your help, Navver thanks so much for explaining it all to me, I think I get it now and I've read a bit about micro switches. If you do have a microswitch how does the tap know when to tell the pump to pump? If that why I seem to have a foot pump and an electric pump in my caravan?
Johnnie Boy thanks for that, I have a look and Hoxelock do one that seems quite good, was would the pressure be like wold you know? I think if I got something like that I'd just get a utility tent and put it outside and then free up the bathroom for storage - we have 2 kids and it's a 4 berth so space always at a premium!
John4703 it sounds like we are quite similar, I love my old little van, It's beautiful to look at, really light to tow and move around a pitch, really simple so I don't have to worry about things breaking and it looks great inside and has loads of handy storage features. I couldn't part with her now. Good news about the switch and thanks for a link to a bette one :)
Are you saying you have a foot operated switch for the pump. That was the system years ago and worked well with just the one tap at the sink.
Before that it was either a foot operated or hand operated pump which again worked well and gave dear old Mum a bit of exercise.
The microswitch is a small switch mounted inside the tap which switches the pump on when the tap is turned on.
Each tap will have a microswitch any of which will switch the pump on.
When a microswitch fails we get the odd situation where say the kitchen tap doesn't work but turning the bathroom tap on at the same time makes the kitchen tap work.
A modern pressure switch system is far better though. They use a small cylinder with a sprung loaded piston in as a damper. This fills with water and will keep the system pressurised.
Turning on a tap will draw water from the cylinder dropping the pressure when it is empty. The pressure switch senses the pressure drop and switches the pump on which fills the cylinder again allowing the pump to again switch off.
This may seem complicated but it allows a very small flow of water without the pump switching on and off rapidly. It runs in short bursts every now and again instead.