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air in system


Guest julie blackburn

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Guest julie blackburn
can you help please? we are having trouble with air entering our mh hot water system.it is a trumatic c3402 or c6002, first turning on the hot tap either in the kitchen or in the shower all we get is very little water & lots of spluttering as if it is full of air. turning another tap on helps a little but not much, we have tried turning the taps on slowly but this does not make much difference. this w/e we filled the cold tank up before we went away making sure there was no air in the system put the heater on but it happened again. could the water be going back down the pipes. hope this makes sense. julie
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I find that this always happens when we refill the system after draining down for the winter. Close all taps then open one of the cold ones, it will splutter like crazy for a while then come out ok. Close that one and repeat with each tap in turn, when cold system is clear start the same proceedure with hot taps and shower, it should clear after a while, dont forget to keep replacing water in the tank as you run it to waste through the taps. I often keep my fingers crossed but it has worked for the past 11 years. Regards Ray. Best of luck Ray
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Guest Derek Uzzell
Julie: It's a pity that you have provided no details of your motorhome. If your 'van is fitted with a pressure-sensitive 'diaphragm' water pump, there may be an air-leak somewhere in the hose-run between the water pump and the fresh-water tank. If this leak is outside the tank then one would might expect to find evidence of water leaking through the hose, but, if the leak is within the tank itself (say, where the hose passes through the tank-wall), then water leakage may not be evident. Another (small) possibility is that a fault in the pressure-sensitive pump is allowing water to siphon back through it into the water tank when the pump is switched off for extended periods. I wouldn't expect this to happen unless your motorhome has a water system with an external fresh-water tank that's below the level of the water pump siting. I'd also expect symptoms of the fault to show when the pump operates. If, however, your motorhome has a 'submersible' water pump, then it may be that a fault has developed in a non-return valve in your 'van's water system. When a leisure vehicle is fitted with a submersible pump (ie. the pump is beneath the water within the water tank itself) a non-return valve is needed to prevent water 'running back' into the tank. The valve is usually incorporated in the water pump's casing nowadays, but may be separate on older models. If the pump (or valve) becomes defective then it will require replacement. When a leisure vehicle is fitted with a Truma C-Series heater, a reliable (and minimum mess) technique to fill the water system after drain-down is as follows: 1. Shut water-system drain-valve(s). Fill fresh-water tank. Ensure all (shower, sink and wash-basin) water taps are turned completely OFF. 2. Switch ON water pump at control panel. (If the water pump starts up then allow it to run until it stops.) 3. Take deep vessel (eg. a small bucket) and place shower-head in it. Turn on shower HOT-water control and direct air/water from shower-head into the bucket until water flows smoothly without spluttering. (The Truma Combi's 12litre water capacity means that it will take several minutes before all air has been expelled and the heater is completely filled.) 4. Empty bucket and then deal similarly with wash-basin and sink hot-taps. 5. Finally deal individually with the shower cold-water control and wash-basin and sink cold taps.
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Guest Brian Ramsden
I fyour system has a pressure sensitive pump and the spluttering persists even after the pump has been working for a while, then the problem could be that the filter on the inlet to the pump is partially blocked. I speak from my own recent experience. I had the same problem and was amazed at the rubbish that had accumulated in the filter. If it is a Surflow like mine, then it is very easy to fix. Drain down the system completely, unplug the two electric wires (one unplugs from the pump, but the other needs to be disconnected at the other end from the pump). Unscrew the waterpipes where they join the pump then take out the screws holding down the pump. Lift out the pump. On one side there is a large transparent plastic chamber to which the inlet pipe was attached. Carefully unscrew this - it is held by plastic lugs and if it hasn't been moved for years it will initially be tight. Hot water and washing up liquid may help, but don't apply too much pressure or you will crack the plastic. When you have removed it you will find it encloses a filter which should be cleaned and replaced. also wash out the inside of the filter chamber. Hope this is helpful. Next week I will find out if this was the complete cure for our spluttering. Brian
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Guest Brian Kirby
Difficult to understand the exact circumstances or extent of the spluttering, but ours behaves in what I think is a similar way. After the cold tank is first filled the air is purged, tap by tap, starting with the cold taps and progressing to the hot taps. Blowing the air from the hot taps does take quite some time though, since the 12 litres of air in the Truma must first be driven off. After a while, though, both hot and cold taps begin to deliver a clear stream of water. However, no matter how much care/time is taken over purging the systems cold, after driving the van and then turning on the hot water, there is always a further episode of spluttering as the first of the hot comes through. I think it's just that small amounts of air remain trapped in the hot water system, no doubt due to pipe alignment somewhere, get stirred around while driving, gravitate into the Truma, and then expand when the water in the Truma is first heated. Once this air has been driven off, all settles down and the system delivers a steady flow of hot without further problem. If your hot water system continues to deliver air beyond the first day of use, then there is almost certainly a more serious fault such as those already suggested. Hope this helps Brian
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Guest julie blackburn
Van make is Dethleffs T5841L year 2004. I will pass all this information to my man who is at work at the moment. I went to have a shower in the van on Saturday there was plenty of spluttering but no hot water (the heater had been on all night) it was as if the hot water tank was not full, we thought the reason it was not hot was because perhaps the tank had not filled itself fully after being used on Friday night therefore the heater would not work properly although I had used it on Friday night to wash up etc. Used the water on and off all day it was not too bad. julie
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Guest Derek Uzzell
I've looked at a 2006 Dethleffs motorhome brochure. This indicates that the type of water pump fitted varies according to the model of motorhome, with either a Shurflo pressure-sensitive water pump OR a submersible pump being used. However, the specific models that have each type of pump are not stated. Probably the simplest way to confirm which type of pump a motorhome has is to remove the inspection-cap on the top of the fresh-water tank and look inside. If there's a substantial cylindrical plastic 'lump' (with an electrical cable leading to it) at the end of the water pick-up hose then that's a submersible pump. Nothing (or just a small filter) on the end of the pick-up hose will indicate that a pressure-sensitive pump is fitted and this will normally be found close to the water heater. Pump noise can also be a give-away - pressure-sensitive diaphragm pumps pulse during operation making a characteristic 'tapping' noise, whereas submersible pumps are near-silent. Your 'no hot water on Saturday' tale strongly suggests that your Truma Combi heater is managing to empty itself somehow. It's possible that the Combi's water-jacket is fractured allowing air to enter, but if this were the case I'd expect to see evidence of serious water leakage beneath the heater. It's also possible that a drain-valve is leaking and in this instance there would be water dripping from beneath the vehicle. In either case, if your Dethleffs had a pressure-sensitive water pump, then you would hear the pump operating when it was switched on but water was not being used. Submersible pumps only operate when a tap is turned on, so, if there's a water leak somewhere, it may be less evident. If your 'van has this type of pump (as seems very likely to me) and you can find no signs of leakage anywhere in the water system, then the non-return valve is the probable culprit. Check this by first filling the water system completely so that water runs smoothly from all taps. Then empty the fresh-water tank and check whether water begins to run back into the tank through the pick-up hose. If it does then there's a non-return valve fault and that's what is allowing the heater to drain. Presumably this has suddenly begun to happen with your motorhome and there have been no problems with the water system in the past?
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Guest Brian Kirby
Just a further thought: if it is a recent problem, it's been quite cold. It isn't the magic Truma drain down valve that has opened during the night is it? That would have drained the Truma water heater a treat and, to the extent the water heater would then be empty, would lead to no hot water available and a lot of spluttering as the pump tried to re-fill the Truma with the drain cock still open. Worth checking? Brian
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Guest julie blackburn
No it wasn't the drain valve we know from a previous experience about that little darling. To be truthful this is our first venture into m/homes and even though we have caravanned for years we have never come across this problem before but then again we have never had an on board water tank and I know you may be thinking "well its only the same as an aqua roll and submersible pump" but to us it ain't, give us a few years and we will look back on this and laugh, because there is no way do I want to go back to a van. I think m/homing is the best thing since sliced bread. Will let you know how we go on. Thanks a lot. Julie
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Guest Derek Uzzell
I had a feeling you might be new to the motorcaravanning game. As you've realised, motorhomes often differ technically from caravans. That's why I always recommend that anyone buying a motorhome for the first time (or even considering buying a motorhome) should obtain the current edition of John Wickersham's "The Motorcaravan Manual" (Haynes Publishing). I'm not sure this would solve your particular problem, but the 14-page chapter on motorhome water systems does refer to the different types/characteristics of water pumps and mentions non-return valves.
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