Water leak when pump turned on

Just arrived on a site and turned on pump in Nuevo. Water leaking from underside of Motorhomes. Stops when pump is switched off.
Any ideas.?

Allistair

Found the answer on the forum. Leak stopped.

Dump valve not closed? We have all (mainly) done it.

Opens at 3C from memory. Closes at 7C from even more distant memory. Or, of course, when you close it manually.
Pre departure checks!
As Peter says, most of us have been there, done that!!

Does anybody know whether these dump valves are prone to opening randomly at higher temperatures? Switched the taps on today to check all was working and water was dumped from under the van so the valve was open. Could the valve have been open for a while but only dumped water when a sink tap was turned on?

IanH wrote:Opens at 3C from memory. Closes at 7C from even more distant memory. Or, of course, when you close it manually.
Pre departure checks!
As Peter says, most of us have been there, done that!!

Not "closes" but "can be closed".
It will open automatically but has to be closed manually and cannot be closed below 7C.

3c opening and 7c closing are internal van temperatures, not external ambient temperature. If water system not drained down for winter this is reason some people use oil filled radiator to keep internal temperature above 3c.