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trail king 7 shurflo pump


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My pump seems to be producing too much pressure. it' s blown the dump valve as their is a constant leak and valve vibrates when touched. in line pressure tank seems full as well./// any thoughts or just change the dump valve?
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Welcome to the Out&AboutLive forums.


It could be helpful to have details of your motorhome (make, model, year of manufacture) as this might reduce the need for guesswork.


The Shurflo Trail King 7 (7 litres per minute ‘throughput’) is marketed in 30psi or 20psi versions, though the latter is probably the most common in motorhomes. In either case, though, it’s doubtful that the pump will be capable of pumping water at a higher pressure than it was designed to do.


When you mention the “dump valve” I assume you are referring to a Truma safety/drain valve. There is a manually-operated version of this, but the automatic version is more common - either the current non-electrical “FrostControl” valve or its electrically-operated predecessor that is no longer manufactured. These valves are designed to open if the pressure in the motorhome’s water system becomes excessive, but this should only occur at well above the 20psi/30psi pressure a Trail King 7 should operate at. If the pump were actually producing a very high pressure (ie. a pressure high enough to cause the safety/drain valve to ‘blow’ and relaese pressure as it’s designed to do) I would have thought you would notice this whenever a tap is turned on. Similarly, if your Shurflo pump were failing to shut off when it had brought the water system up to pressure, I’m pretty sure you would have said so.


I’m guessing that your “in line pressure tank” is a ‘surge-damper’ of some sort as shown in photos here




I can’t really comment usefully on your suspicions that this seems full (ie. if the tank is a surge-damper with an internal diaphragm, that the diaphragm has ruptured) but even if that had happened I would not see it being a direct cause of the valve leaking.


You could try opening and closing the drain valve several times, just in case some debris has found its way inside and is preventing it from sealing properly. The flow of water through the valve might then flush out the debris. My understanding is that an electrically-operated Truma safety/drain valve cannot be disassembled, repaired or adjusted, though this is apparently possible (to some degree) with the current FrostControl valve.




Over the years there have been quite a few inquiries here relating to leaking Truma safety/drain valves and (as far as I can recall) the solution has always eventually involved valve replacement. As your valve is leaking constantly, if the opening/closing ploy doesn’t help, I believe you will need to replace the valve.


As I said earlier, Truma’s electrically-operated safety/drain valve is no longer in production and, if that’s what you currently have, you may find it extremely difficult to source a like-for-like replacement. The options then would be to replace your current valve with a manually-operated one or the FrostControl valve.



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Derek has given excellent advice but I would just add the following which may be vaguely related to the OP's problem.


There should be a pressure release valve (PRV) near the top of the water boiler. This is connected to a small bore diameter plastic pipe which quite often exits the floor of the van near the dump valve. So, if looking beneath the van for the water leak, it could possibly be coming from the PRV.


The pressure release valve can also get grit in the valve and prevent it from closing properly. The valve can be removed and cleaned but don't remove it when the boiler is under pressure or has very hot water in it. I seem to remember the valve just needs to be turned through 90 degrees and it pops out.

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sully - 2015-08-20 5:04 PM


many thanks replacing the valve today although the old one seems to work doing a suck and blow job although i cant blow at 20psi will keep you informed for others to follow. many thanks for advice. (!)

All quiet on the western front touch wood now fitted new valve. Many thanks for your help. My motorhome by the way is a 2001 knaus sunliner. Excellent build quality put together by midgets that crawled into the smallest crevices to hide all the pumps and valves. Happy days
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