Cold Water Running Hot!

Aug 6, 2020
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Hi,

We have a 2016 Lunar Venus 580 which we love.

We have a problem with the cold water feed to the kitchen tap whereby the water runs alternately hot and cold for at least 30 seconds. The issue is caused by the hot and cold plastic pipes being clipped together on their path from the inlet. Where they touch the hot pipe heats the water in the cold pipe. I have separated the pipes in as many places as I can easily get to.

Has any one else experienced anythingsimilar and found a solution? Is it possible to buy insulation for the 12mm pipes to prevent this happening?

Thanks in advance for any suggestions.

Steve
 
Mar 27, 2011
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Just let cold tap run obviously it only takes 30seconds for the warmed cold water to be run off the pipe, a lot easier than insulation do you not think and no cost
 
Sep 16, 2018
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Yes, we have this both in the caravan and at home. To be honest it's never really bothered us but a quick Google search found loads of flexible 15mm insulation if you want to fix it.
 
Aug 6, 2020
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Just let cold tap run obviously it only takes 30seconds for the warmed cold water to be run off the pipe, a lot easier than insulation do you not think and no cost
But we end up running through 10x more water to clear the hot patches than we actually need to use! And of course the Aquaroll needs filling more frequently and the waste fills up much quicker too.....
 
Aug 6, 2020
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Yes, we have this both in the caravan and at home. To be honest it's never really bothered us but a quick Google search found loads of flexible 15mm insulation if you want to fix it.
Our pipes are 12mm plastic which I struggled to find a fit for with insulation. Some of the pipework is going to be difficult to get to as well! I might wish I'd never started!!
 
Nov 11, 2009
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Can you not get duplex pipe supports that will physically separate some or all of the pipes length, but not have them screwed to a hard surface. The ones below are 12mm.

F3F76F60-74B3-42A9-AF83-032AF2F24974.jpeg
 
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Mar 14, 2005
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Hello SteBur,

There is a well known alternative explanation for alternating pulses of hot and cold water.

From your description I would guess you have a pressure switch that controls the pump. This can lead to a strong cold water delivery which even though the tap is open the pump is strong enough to build up enough pressure to cause the pressure switch to turn off momentarily.

The hot water tank is designed to have an air cap, this is to allow space for the water to expand as it heats. but when the cold water is pushed in, the cap is pressurised. The the pump turns off, the air cap can re expand and push hot water out in to the pipework. It continues to do this until the pressure reduces enough for the switch to re connect the pump and reestablish the cold water flow.

This was particularly a problem for mixer taps, but it can happen for separate cold taps also if the water heaters non return valve in the cold feed has been damaged and is not resealing correctly. Hot water can be pushed back out of its cold water inlet which the joins the flow in the cold pipework.

There are a number of possible solutions, First you should check the adjustment of your pressure switch, - see the manufacturers instructions for teh pressure switch,

Secondly check teh water heaters non return valve is functioning.

The the problem continues, you may need to get a surge damper fitted to the cold water pipes, or if you have a Whale submersible water pump, Whale have a "Watermaster IC Pump Controller " which helps to smooth out pressure fluctuations.

There is no harm in separating the pipes, but I'm not sure it will have the desired effect for you.
 

Mel

Mar 17, 2007
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Coming at this from another angle: why is it a problem? Is there an easier way to solve the problem this creates than major engineering?
Mel
 
Jan 3, 2012
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Why don"t you take it to someone who knows how to repair it a caravan dealer or a Mobile caravan repairs who will come and fixed where the van is ..
 
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Damian

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Mar 14, 2005
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I hate it when overly complicated "solutions" are posted for a simple inconvenience.
It has been common for a very long time that when installing the pipework the hot and cold pipes are run alongside each other, and heat transfers from hot to cold supply along various places, especially where the pipes are in enclosed locations.

Whilst it may be slightly inconvenient it is not a huge problem.

You know it does it so just use the cold tap first and if required, save the water for washing up as it will be slightly warm, so reducing the amount of hot water used a little.

If you want to drink the water, then even the cold will not be that cold after sitting in an aquaroll for any length of time, so a better option is to have a container of water in the fridge.

Quote " Why don"t you take it to someone who knows how to repair it a caravan dealer or a Mobile caravan repairs who will come and fixed where the van is . "

There is nothing to fix !!!! unless the engineer is to completely re route the water system,,,,,,,not practical and not needed.
 
Jan 3, 2012
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i am fully qualified Chef i dont touch anything on my caravan i dont know what i am doing so anything with my van that is where i will take it Damian you should know that your trade engineer .
 
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Damian

Moderator
Mar 14, 2005
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i am fully qualified Chef i dont touch anything on my caravan i dont know what i am doing so anything with my van that is where i will take it Damian you should know that your trade engineer .
I quite agree, if you dont know how to do something, get someone who does.

However, in the case here there is no fault to fix, its just the way vans are made and have been for decades, and I cannot see the makers changing their way of doing things.
Just bear in mind that the people putting the van together have 10 minutes to fit all the plumbing, gas, water and electrics.
 
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Jan 3, 2012
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Well i am making notes how some things need fixing but it will take me longer than 10 mins to fit the plumbing, gas, water, & electrics because i am a beginner ,
 
Aug 6, 2020
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I have been continuing my reaseach in to the hot water in the cold tap problem and it turns out there are actually 2 problems with the plumbing in our caravan:

1: Looking at the diagram in the manufacturer's handbook that came with the caravan, and comparing it to the actual plumbing, they are not the same. The caravan does not match the plumbing diagram and the T piece that splits the cold water feed from the pump into 2 - one for the cold taps and one to the water heater - is in the wrong place.

2: There is no non return valve in the system at all. Whilst this does not appear in the manufacturer's plumbing diagram, it is mentioned in the accompanying text with details of where it should be fitted in the pipework. This detail is backed up by the detail in the paperwork for the installed Truma Ultraflow system.

Basically, the T-piece hot/cold splitter should come before the heater drain valve going in the direction of the water flow, but ours is fitter after the heater drain valve. Then the (missing) non return valve should come after the T-piece splitter and before the heater drain valve and heater thereby preventing the higher pressure (~60 psi) hot water from the heater getting back into the cold water pipework which is at much lower pressure.

Hopefully a minor change to the pipework and the addition on the missing non return valve will cure the problem. Having 70C hot water coming out of the cold tap is not ideal!!
 
Mar 14, 2005
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I agree with your assessment of the correct arrangement of Tee piece NRV and drain/safety pressure valve.
 
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Aug 6, 2020
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I hate it when overly complicated "solutions" are posted for a simple inconvenience.
It has been common for a very long time that when installing the pipework the hot and cold pipes are run alongside each other, and heat transfers from hot to cold supply along various places, especially where the pipes are in enclosed locations.

Whilst it may be slightly inconvenient it is not a huge problem.

You know it does it so just use the cold tap first and if required, save the water for washing up as it will be slightly warm, so reducing the amount of hot water used a little.

If you want to drink the water, then even the cold will not be that cold after sitting in an aquaroll for any length of time, so a better option is to have a container of water in the fridge.

Quote " Why don"t you take it to someone who knows how to repair it a caravan dealer or a Mobile caravan repairs who will come and fixed where the van is . "

There is nothing to fix !!!! unless the engineer is to completely re route the water system,,,,,,,not practical and not needed.
I think you are underestimating the scale of the problem. We appear to have 70C hot water straight from the heater coming out of the cold tap making the cold tap in the kitchen unusable at times.

If you check out my post later in this thread you will see that I have identified that there is a problem with the way the caravan was plumbed in the factory
 
Mar 14, 2005
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From your last post I think you have found the cause and solution to your problem.

Just for your information and anyone else who may have hot cold mixing problems, there was another quite common problem where the hot water tank was hot, but people only got warm water at the taps.

It was quite common for caravan manufacture's to fit a shower with a trigger controlled shower head. This only controlled the flow of water through the head, not the temperature. The user had to adjust a simple mixer tap to get the desired temperature. It was far from uncommon for the mixer tap to left set, and the trigger control was relied on to stop the water flow when the shower was finished. Unfortunately, the mixer valve's were effectively connecting the hot and cold services, and it meant that any tap in the caravan would cause both hot and cold to be mixed at the shower mixer and because they were at the same pressure, it would and feed back to all taps.

The solution was to fit NRV's to the hot and cold services to the shower mixer. Some caravan manufacturer's took some convincing it was their design and choice of components that was to blame.
 
Jun 20, 2005
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Thanks to Covid it has taken me this long to respond🤪see these pics. I had this trouble 11 years ago . Consulting forumites here and elsewhere the solution was NRVs and two drain taps. See the pics. Never looked back. Note the white pipe with the NRV and how the interface between the hot and cold feeds is now plumbed and semi by passed. Hope this helps those with older units.
 

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