2012 Nuevo water System Pribkem

Hi
I bought a 2012 Nuevo ES in January and am now preparing for our first trip. When I bought the van, the water system was loaded and I drained it down, including the Truma boiler, to protect the system for the remainder of the winter. I refilled the system a couple of days ago and I have a problem with an airlock which only affects the hot water taps. When I run the taps for a few minutes the airlock clears, after much spluttering, and water runs freely.  However, the pressure switch & I presume pump, kicks in every few minutes and pulsates a lot.  When I switch the power off overnight the airlock is back in the morning and the pump just runs continually. When I run the hot water taps for  a few minutes the airlock will clear again.  The water pump is in the tank and the pressure switch is housed on the floor under the offside rear seat.  I appreciate that much has already been said about this type of water system but I can’t find anything with my specific problem.  Any help would be appreciated

Norris looks like you have either got a leak in the hot side of your system , pipework connections or boiler. If nothing visible it maybe the pressure switch which has a non return valve  built in . If this is not sealing properly due to a bit of dirt or grit it will allow water to leak back into the tank as system will not sustain pressure giving exactly your symptoms. Take out the pressure switch and remove the 2 screws at the input side . The valve is a small rubber disk held closed by a spring. Clean the assembly and that should hopefully sort your issues.

Thank you both so much. This is my first time posting and much impressed!!
I did as Kaspian suggested and problem solved. System now working a treat.

Thank you again

Wow that was quick!  Glad you got a cheap fix and you now know what to do in future.

I spoke too soon! System started playing up again after a couple of hours i.e pressure switch activating every few minutes and hot water taps full of air when system switched off overnight.. I took the switch apart and gave it a clean, although I couldn’t see any obvious signs of dirt. I have also checked all pipe work from pressure switch back to boiler and couldn’t find any sign of a leak. Just wondering if I should just replace the pressure switch. They are reasonably priced on Amazon at £25.

Is your hot water drain tap leaking?

It's not unknown for a bit of plastic swarf or other detritus to get under the seal and allow a small leak.

Gromit - not sure what you mean by hot water drain tap. Is it the boiler dump valve.

Norrie if you are sure that the one way valve in the pressure switch is clean and the rubber seal and nylon nozzle it seals against is undamage then it can really only be a small leak somewhere in your hot side of the system. It only takes a very small leak as Gromit says from the dump valve or a hidden connection like behind the shower valve or bathroom / kitchen tap . If the boiler is having to refill in the morning after sitting overnight I would guess at the boiler pipework or dump valve.  It could be dripping unseen under the van especially with the system hot going unnoticed. The way the system is pressurised there will always be the odd turn of the pump while lying idle  as hot water cools in the boiler and pipework etc but if it it running regularly with no demand then (if adjusted correctly ) the pressure is dropping and water going somewhere....

Thank you kaspian. Would I need to remove the dump valve to clean it?  It looks like a sealed unit to me.

On the Truma boiler there is a small take off pipe from the hot water feed. This consists of a one way valve, item 15 in the pic, and a clear pipe, item 20, that is directed under the van.
The purpose of this is to let air into the boiler when you open the dump valve. It's far better to open the hot taps when you do this, otherwise grit can be sucked up the dirty clear pipe pipe and into the valve, causing it to fail.
This happened with my system. Replacing this small valve assembly cured the problem.
The moral is, always open your hot taps when draining down the boiler.
Al.

Thank you bikeralw. Will try that as there doesn’t appear to be a leak anywhere. Checked round boiler, taps, dump valve pressure valve. Also checked under van and can’t see any drips. If I switch the system off for an hour the hot water taps are full of air.

Any idea where I can source the valve you refer to.

Here, but please check your system, mine was for a 2004 van. I have no idea if things changed on later vans.
https://www.ebay.co.uk/itm/GENUINE-Truma-Combi-Ultrastore-Water-Heater-Elbow-Valve/114251052382?epid=2214432284&hash=item1a99e4b55e:g:9MIAAOSw161e2-xI 
Al

I removed the valve shown at 15 on the diagram and it seems to work ok (opens when I blow and closes when I suck!). Had another look at the pressure switch and noticed that the edges of the rubber seal, referred to by Kaspian, are curled up. Does anyone know if it’s designed like that or is it just worn.

Sounds like that may be your issue as I said. To confirm you could fill and pressurise the system then remove the pipe connection on the input side . If water weeps past the valve over time then that is your problem confirmed.

Thank you Kaspian.  You’re right - steady trickle from switch when I removed inlet pipe. Will order new switch.

I think you can get a service kit with new seals and switch around £13