Shower Temperature Control
2013 Swift Challenger 524 Sport, Truma Combi 2E. Caraflo Manual Mix Shower Tap. We've had the van for 7 years now. We use the shower in the recommended manner i.e. on to wet all over, off to soap all over, on to rinse etc. One thing bugs us. We set the mix to an acceptable temperature. Each time we turn off and then back on again ( it can be a matter of seconds) we initially get cold water and then it resumes to the pre-set temperature. It's as if the hot is held back momentarily, but how. The mixer valve doesn't seem to be anything special e.g. excessive temperature safety device. The hot water doesn't have time to cool down. We have plenty of hot water in hand.
Is this just normal, am I missing something?
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We have a Swift Group caravan, 2008 twin axle model, we also use our own shower most of the time, in the manner you describe.
Our heating and HW is via an Alde boiler, and the water temperature behaves in the exact manner you have described, so I think this is normal. The hot and cold are not at the same pressure, with the cold having a slightly higher pressure, so it gets through first when the tap is turned back on
Once you have had a few seconds of cold water hit you, you soon learn to take the shower head down and direct it elsewhere when you turn the water on again!
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Very normal situation as described, same situation at home except for the luxury of leaving the shower running for longer.
I think it is just a case of the hot water in the shower hose cooling down while it is not being used. Also the feed pipes are small diameter and the hot pipe can cool down from the 50° (or so) start temperature very quickly so getting back to the set temperature can take some time.
Not sure that I understand how there can be a pressure difference in the hot & cold supplies as they are both fed from the same pump.
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It is complicated, and I am no expert, but there will be a pressure difference when the water is flowing due to the HW pipe being longer than the cold. The number of bends and T-pieces also makes a difference.
Due to the larger mass of water in the hot pipe it will take a little longer to start flowing again, so it takes a few seconds to return to the set temperature.
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Im not sure how long you have the water turned of between soaping up and rinsing off, but the water shouldn’t cool that much in a few minutes.
The answer is to replace the standard mixer with a thermostatic controlled one. I did this on my Bailey unicorn 3 and once the water is run through to the shower it maintains this during the showering process of on off on operation. Considering the cost of caravans and motor homes i do not understand why these are fitted as standard. Would be a lot safe as well.
Mine was fitted from new in 2015 and is still giving reliable service.
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