External 12 volt water pump keeps failing

Just after we took delivery of our van, I changed the external (Truma) and internal (Reich) pumps to Whale High Flows and the flow rate and pressure was much improved.  In nearly 5 years of quite heavy use, I've not had a problem - but I always carry a spare!

From what you say, you're not exactly experiencing a 'failure' and it sounds more like a blockage to me - especially as you say you don't use the van that much and algae etc could have built up. It could also be air in the system - possible causes include failed "O" rings at the connection.

It's difficult to say without hearing the pump in action - does it run at normal speed even though delivering a reduced flow - or is it slower? If so, it could be an electrical problem, although that said, they tend to either work - or not. If it's running very fast with little output, then I would definitely be leaning towards air getting in the system.

Sorry, don't know what else to suggest but I'm sure others will be along with their ideas.

It is definitely the pump which fails as when I purchase a new one and test it by not connecting the outlet to the caravan it will pump the water from an aqua roll in a water jet (like a hosepipe) for about 12 feet. When it starts to fail it falls back to about 3 feet so a loss of pressure. This means when the pump outlet is connected to the caravan inlet there is insufficient pressure and water flow. It seems as if the pump weakens, possibly the rubber diaphragm.

I think the best solution is to follow your example and fit an internal Whale High Flow pump so many thanks for your post.