Different fresh water systems

[AlanD]

Could someone please explain (in easy terms) what the difference is between a pressurised and a non pressurised system and which is the best? Thanks in advance

 

[GEOFF]

In a pressurised system (PS) the water pump keeps the system under a preset pressure and switches on and off to maintain that pressure. Opening a tap allows water to flow and the pump detects the fall in pressure and switches on to recover that pressure, thus keeping the water flowing. Turn off the tap and the pump will recover the system pressure and switch off. In an unpressurised system (US) the pump is switched on when the tap is opened, and off when closed. This usually means that each tap has a circuit to switch the pump on. The PS is now normally the preferred option. I hope that makes sense. Geoff.

 

[Squiffy]

I would just add Geoff that with a pressurised system you can use any type of household tap as opposed to having to use a specific electronically switched tap in a unpressurised system which invariably stops working and the switch requires replacing at the most inconvenient time. Phil

 

[Millie Master]

When I was a tugger the water systems fitted to the vans proved oh so very often to be an absolute pain with the Whale pump constantly switching on and off and a frequently pulsating water supply which made showering a very unpleasant task!

So I fitted a constantly pressurised system with an inline Shurflo pump and (as Squiffy has suggested) domestic taps that are of a far higher quality and far cheaper price than those made specifically for caravans and boats.
In my experience it has proved to be totally foolproof, whereas from my past experiences a switched unpressurised system isn't!

Phil

 

[AlanD]

Thanks for your answers, so pressurised seems to be the best. Can I use flexible tubing or is domestic push fit better?

 

[GEOFF]

Many people use the domestic push fit. I personally prefer to use the red/blue food grade flexible hoses. There is nothing wrong with either system IMHO, but the flexibles need barb type connectors. Geoff.

Thanks for your answers, so pressurised seems to be the best. Can I use flexible tubing or is domestic push fit better?

 

[AlanD]

Thanks again and apologies for what must seem very basic questions to most of you.
Looking online, Shurflo seem to be the most popular pumps but some recommend using them with an expansion tank, is it essential to use one?

 

[Squiffy]

I have never used an expansion tank Alan and never had a problem, in fact I bought one for my latest van build which was about four years ago and ended up giving it to someone on the DIY site. I think it would make a difference if the water pipe installation was of excessive length but for the average motorhome it isn't required. Phil

 

[GEOFF]

I use an exp. tank on the hot water circuit, but not the cold. An exp. tank should stop any "pulsing" while the water is flowing. Geoff.

 

[IJenk52]

I put in a "T" off the pipe after the pump and ran a piece of plastic pipe to a length of 1" copper pipe, blanked off at the top, vertically at the back of the wardrobe. It was full of air 'cos the water couldn't get out at the top and it acted as a buffer to stop the pulsing. Making the pipe run all uphill prevented the trapped air escaping and any water ran out when draining the system down. No maintenance needed and cheap 'cos I used bits I already had.
Hope that makes sense.

 

[wildebus]

I use an exp. tank on the hot water circuit, but not the cold. An exp. tank should stop any "pulsing" while the water is flowing. Geoff.

This is what I would go along with. I fitted my expansion tank (aka Pressure Vessel) on the water circuit going INTO the water heater though so it is essentially on the general supply and hence works on both hot and cold runs. If you have a pressurised hot water heater then a Pressure Vessel really is a good idea as a precaution (maybe a bit overkill on a van using pumped stored water as max pressure is limited, but a worthwhile precaution IMO).
It also helps pulsing as said above.

This is my own setup. I also went belts & braces with a pressure release valve (as I had it anyway and also can work as a drain cock)

Clarence Water by David, on Flickr