Truma water heater

[Ginge@72]

Hi All
Looking for some advice. We have a 2006 swift challenger 530, on the last few outings the hot water side of the system continues to air lock/spit & splutter after each use, every time we want to run the hot water tap we have to continuously pull through again and again until the water flows freely again. I have changed the hot water valve on the tank (red & white one with breather pipe) but still not solved the issue…

Any advice would be much appreciated if someone knows a trick or two to solve it.

Many thanks
Chris

 

[ProfJohnL]

The symptom you describe suggests the contents of the hot tank is emptying . but the water must be going somewhere. Is there any evidence of a leak under the caravan?

If there is no obvious leak, then it suggests the content of the hot tank is flowing back through the pipe work probably to the cold water barrel. For this to happen there must have been two non return valves fail. Has the caravan been left with water in the pipe work over winter? if so its possible that the NRV's may have been damaged by water freezing in them, causing them to fail.

 

[Ginge@72]

The symptom you describe suggests the contents of the hot tank is emptying . but the water must be going somewhere. Is there any evidence of a leak under the caravan?

If there is no obvious leak, then it suggests the content of the hot tank is flowing back through the pipe work probably to the cold water barrel. For this to happen there must have been two non return valves fail. Has the caravan been left with water in the pipe work over winter? if so its possible that the NRV's may have been damaged by water freezing in them, causing them to fail.

Thanks for this. The van has a full drain down for winter and is stored inside over winter so frost probably not the issue. I will check for leaks under the van, not evident inside. I will replace both valves on the tank too see if this works, so they are both non return?

Many thanks for your reply!

 

[ProfJohnL]

As you haven't told us the exact model of water heater you have (Truma have made several different models over the years) I will assume it is an Ultrastore 10L gas and electric heater. You will find a set of operating and installation instructions here

Having drained over winter, did you close the floor mounted safety /drain valve? The lever should be horizontal for closed. If its upright then it will be constantly draining leading to the symptoms you describe. You may also have damaged the heater if its been run up whilst little or no water is in it.

If the valve is closed, and there are no obvious leaks, then the water must be draining back into the cold water pipes, and possibly back into your cold water tank. If this is happening then it means the NRV in the cold pipe work where the water enters the caravan is not working.

 

[Ginge@72]

As you haven't told us the exact model of water heater you have (Truma have made several different models over the years) I will assume it is an Ultrastore 10L gas and electric heater. You will find a set of operating and installation instructions here

Having drained over winter, did you close the floor mounted safety /drain valve? The lever should be horizontal for closed. If its upright then it will be constantly draining leading to the symptoms you describe. You may also have damaged the heater if its been run up whilst little or no water is in it.

If the valve is closed, and there are no obvious leaks, then the water must be draining back into the cold water pipes, and possibly back into your cold water tank. If this is happening then it means the NRV in the cold pipe work where the water enters the caravan is not working.

Thanks, heating up well no issues with getting hot water and always check we have a full tank before switching water heater on. Drain down lever is always closed obviously when we arrive on site and fill the system. I will check as the drain down valve isn’t failing a still allowing water to drip out, we’ve had failure in the past when the tap wouldn’t close and has been replaced.

I will change the cold water NRV to see if this is the issue which I suspect is….
Will let you know when we’re home to replace next week.

Thanks again!

 

[Ginge@72]

As you haven't told us the exact model of water heater you have (Truma have made several different models over the years) I will assume it is an Ultrastore 10L gas and electric heater. You will find a set of operating and installation instructions here

Having drained over winter, did you close the floor mounted safety /drain valve? The lever should be horizontal for closed. If its upright then it will be constantly draining leading to the symptoms you describe. You may also have damaged the heater if its been run up whilst little or no water is in it.

If the valve is closed, and there are no obvious leaks, then the water must be draining back into the cold water pipes, and possibly back into your cold water tank. If this is happening then it means the NRV in the cold pipe work where the water enters the caravan is not working.

Ps it’s the old 10L gas & electric tank.

 

[Dustydog]

Look to where your aquaroll water feed to caravan pipe enters the caravan . It could be a Whale or Truma. Both contain a number of O rings which wear with time and allow air into the system. When you open the hot tap ,cold water is drawn into the Truma water heater boiler. If the O rings are faulty air will be drawn in giving the symptoms you describe.
Change all the O rings. If that doesn’t cure the problem then look elsewhere .

 

[Ginge@72]

This is my system
Is the 12mm blue valve by the drain down valve a non return? Thinking this could be the issue. And are the elbows on the tank also non return or not?
Thanks

 

[ProfJohnL]

Thank you for the pictures.

They confirm you have an Ultrastore.

I cant see any sign of a pressure switch to control the pump, so I'll guess the pump is controlled by micro switches in each tap. This does make a small difference, as when you are not using any water, the cold water pipe work is not held under any pressure. This means if the cold water non return valve is not working properly and it is allowing hot water to drain back into the cold supply pipe, there is no pressure in the cold system to oppose the hot water.

We must also consider that as the heater warms the water in its tank, as heats it also expands a little which compresses the small air cap at the top of the tank. this will normally ensure the hot water covers the outlet of the tank and will deliver water but air If the NRV is not holding the pressure the air cap will also expand and push the hot water out through the tanks cold inlet, and the level of the water in the tank may well drop below the tanks outlet pipe meaning it will deliver some air before hot water when a hot tap is opened.

I can see from the pictures the drain port in the blue pipe and just upstream of the drain valve there is a blue straight section which is almost certainly the NRV. Either the NRV is not locking off, or the drain valve is leaking below the caravan.

 

[Ginge@72]

Thank you for the pictures.

They confirm you have an Ultrastore.

I cant see any sign of a pressure switch to control the pump, so I'll guess the pump is controlled by micro switches in each tap. This does make a small difference, as when you are not using any water, the cold water pipe work is not held under any pressure. This means if the cold water non return valve is not working properly and it is allowing hot water to drain back into the cold supply pipe, there is no pressure in the cold system to oppose the hot water.

We must also consider that as the heater warms the water in its tank, as heats it also expands a little which compresses the small air cap at the top of the tank. this will normally ensure the hot water covers the outlet of the tank and will deliver water but air If the NRV is not holding the pressure the air cap will also expand and push the hot water out through the tanks cold inlet, and the level of the water in the tank may well drop below the tanks outlet pipe meaning it will deliver some air before hot water when a hot tap is opened.

I can see from the pictures the drain port in the blue pipe and just upstream of the drain valve there is a blue straight section which is almost certainly the NRV. Either the NRV is not locking off, or the drain valve is leaking below the caravan.

Many thanks for the informative response. I’ll change the blue NRV. Valve by the drain down valve. I’ve placed a bucket under the drain down valve to see if any water is escaping from this also but I suspect the NRV is the issue. And correct in guessing each tap has a micro switch.
Thanks again for this helpful advice, narrowing it down for me to resolve is great!