Hot water supply problem

This is my first message and a pleasure it is to know that there are people out there who may be able to help.

Due to a difficult summer for many personal reasons we used the camper in anger last July and that is the last time I recall the hot water system working. We have done day trips but not used the hot water heater, but we have used cold water which has been fine.

A couple of weeks ago I decided to make sure the hot water system was emptied fully in case of a frost and went about the usual things expected when winterising the van.

However yesterday we went for a more adventurous and lovely day trip out to Llangorse lake. My partner was in full bake off mode and we needed some hot water to wash up with. 

As it had been winterised I only filled up half the fresh water tank and didn't, as I normally do, run the hot water tap in the kitchen area to make sure the carver rapide water heater and take (which has a 9 ltr capacity I think) is fully loaded. I have found on wild camping trips that almost a quarter of the fresh water is lost if I don't do this and then top up the fresh water.

Any who I'm getting distracted now. The point of this post is I turned on the cold water tap at Llangorse lake and all fine. I turned on the the hot water taps and nothing happened. I tried all the hot water taps and still the water pump didn't activate.

at the kitchen sink I turned on the cold water tap, then the hot water tap. The flow decreased in pressure to maybe half the flow rate. I then turned off the cold tap fully with the hot tap fully open. The tap continued to allow water to flow until it stopped but the pump was not activated. It had stopped when I turned the cold tap off.

I spoke to a nice chap at Auto Sleeper today who thinks there is a blockage some where and I need to remove the Carver from the side of the van to investigate. 

This is fine but before I start puling things to pieces has anyone else experienced anything similar and have any advice.

Kind of a broad request I know but any hints n tip greatly appreciated.

Hi and welcome to the forum from Bridlington .
Boaby

Hello and from Leicestershire. Sorry cannot help you with your water heater, hope you get it sorted soon,

Hi there and a big welcome to the forum from Filey .

As water actually flowed from your hot taps using the residual pressure built up by the pump into the hot tank I can't see how there can be a blockage.  The problem seems to be the pump is not activating when you open the hot taps. I don't know your system operation I.e px s/w or micro switches to fault find further but I am sure someone will 

The water pump activates on a drop in water pressure when the tap is turned on and not with micro switches.

In agree with you on the fact a blockage cant be the problem as water has made it out out if the hot tap eventually,

Looking like i have to take the whole system apart, yikes?!?!

Before you strip it down, make sure it's not an airlock - follow this procedure....

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I agree, it's a bit of a strange issue 

An airlock would normally allow the pump to run until sufficient pressure builds back up, but without water delivery and as you say, a blockage would prevent any water being delivered.

Please update once sorted.

Ken.

OK, will explore the airlock option first. Will break out my my divers mask and helmet first and report back. Give me a couple of days on this as got a busy week.

Thanks ken and paulmold for advice so far and anything else welcome.

Iain

Hi and welcome

I wonder if your pressure switch needs a tweak?

Usually when turning on the hot tap the water will run for a few seconds before the pump cuts in. This is obviously due to the built up pressure in the boiler. As it drops the pressure switch activates and turns the pump on.

Since your pump is not cutting in, this suggests to me that the pressure switch is not activating, and has probably become a bit insensitive. Mark its position first of course, and give it a tweak of no more than a quarter turn.
(Bet you turn it the wrong way first! )

This will either work or it won't, but if that is the problem it's a quick and easy fix.

Were you off EHU when you had the problem, and might your battery have been a bit low? These pressure switches are notoriously sensitive to voltage. Before I had a Shurflo fitted (which has its own built in, and far more reliable pressure switch) our submersible pump would work fine on hook up, but on battery power I regularly had to adjust the pressure switch for it to work properly.

Hope I've guessed correctly - 'cos that's really all it is.

Symphonies don't have separate pressure switches as they have Shurflo pumps so can't be that.

They have one built in but not one that's easily accessible and rarely if ever needs adjustment.

Agreed Paul, as I said, but they are not infallible. It's all I can think of to suggest, and even with a Shurflo it's easier than pulling the van apart!  (A lot depends on where and in what orientation the pump is mounted.)

This may be a load of rubbish of course, but my hypothesis is:-

When the cold tap is turned on the pressure drops instantly and suddenly. If the pressure switch is on the limit of functioning or not, the sudden drop in pressure is likely to kick it into action.

When the hot tap is turned on the pressure drops gradually and quite gently. It seems feasible that if the pressure switch is a bit sticky it might stay closed without a bit of a jolt.

It's certainly a puzzle, and a new one on me.

Hope it helps him.

Dave, 
I thought you were more likely referring to the type that is open to adjustment with a knurled wheel on top which you adjust by fingers such as you get with submersible pumps . I've had that type for 25 years in Caravans and they are a real pain to get right.

I was Paul, as I'm not familiar with the van - and yes they are a real pain. You get the damn thing working today, and tomorrow it plays up again, specially when off hook up.

For what it's worth my fanciful theory just could be correct however, even with a Shurflo. I can't think of any other explanation as to why the cold tap would work, but not the hot tap.

The OP appears to be only 44 so he's probably at work. Let's hope he comes back with a final report when he gets it fixed. Who knows - I might be insufferably smug for a few days afterwards!!

One thing Ian could try (as cold seems to work and therefore pump
 px sw ok?) is to open cold tap enough to drop px and get pump running, then open hot and see if it runs while pump is still running? Then close cold and see if it keeps going?
These things are always difficult to diagnose from afar .

Sounds to me like the non-return valve on the carver is stuck/sticking. 
Remove the drain plug and insert a long, thinnish rod. Feel for the non-return valve which is directly opposite the drain plug and give it a push. You should be able to feel it moving. Once you're sure it is moving, refill and try again.

EDIT:
Scrub that! I still think it's the non-return valve but I think you need to push it from the other side 

Frank