Insulating & Heating under-slung water tanks? What's the problem with this?

[Wissel]

I posted a question on a self-build forum about winterising my under-slung water tanks.

My idea was to fabricate a box around them both, insulate it, then run the vans heating through the enclosure. I was asking if anyone had done similar or had any tips.

Firstly, I was warned this would cause bugs in the water. But there are tablets to help with this.

I was then told that even the better coachbuilts don't have this (by another member) and that deadly bugs could multiply in their trillions. I was told to forget the idea.

As two people have told me the same, I think I must be missing something obvious?

I replied that lots of motorhomes have twin floors with the tanks between (with the void heated) and asked what's the difference with vans that have internal tanks?

I've not had an answer.

I know I must be missing something very simple, but I can't see what it is.

Please someone, what am I missing? It's driving me nuts.

 

[tacr2man]

i dont see what you are missing , other than the degree of heating that might be involved if excessive . but if you think of tanks in a void floor in summer parked on bitumen i would think that water could get pretty warm .

 

[Figaro]

Badly informed forum contributors ?
I have twin floor insulated tanks and I`m still alive, no deadly bugs in my water works !

 

[Yorick]

Just buy bottled water to drink

 

[Wissel]

Just buy bottled water to drink

I do

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[Yorick]

I do

Good. Water doesn't have the potential to make it self poisonous and harmful and start murdering kittens.
You'll be reet.

 

[Wissel]

Badly informed forum contributors ?
I have twin floor insulated tanks and I`m still alive, no deadly bugs in my water works !

I'm wondering the same. Thing is I didn't want to just assume I was right after asking for advice.
Hence asking here

 

[CazPaul]

What about having the heating pipes with valves which you can turn on and off. I don't think the fresh water temperature would get warm although not sure. If you have a valve that can be opened when it is freezing so only use it when you require.
Legionella can form when the water is above 20 degrees centigrade, I can't see this being an issue in an enclosed tank that is not open.
Hot water needs to be below 38 degrees centigrade for it to form so the danger zone is between 20 and 38 degrees.
As long as the tanks are flushed out and cleaned then no issue I don't think. Its still, stagnant water with open lids that are the grounds for bugs to breed.
Its easy to test water with a cheap 2 quid bath thermometer. I have to test and record this every week as part of legionella management. All taps and showers are tested weekly and recorded.
As I say cold water above 20 degrees and hot water below 38 degrees are the crucial figures when legionella and other bugs form.

 

[Wissel]

What about having the heating pipes with valves which you can turn on and off. I don't think the fresh water temperature would get warm although not sure. If you have a valve that can be opened when it is freezing so only use it when you require.
Legionella can form when the water is above 20 degrees centigrade, I can't see this being an issue in an enclosed tank that is not open.
Hot water needs to be below 38 degrees centigrade for it to form so the danger zone is between 20 and 38 degrees.
As long as the tanks are flushed out and cleaned then no issue I don't think. Its still stagnant water with open lids that are the grounds for bugs to breed.

I did think about isolating the heating through that area, then figured the heating would only be on if it was cold anyway?

Surely this is the same on any twin floor motorhome? Or is there a gizmo I'm not aware of fitted on these vans?

Thanks

 

[CazPaul]

I did think about isolating the heating through that area, then figured the heating would only be on if it was cold anyway?

Surely this is the same on any twin floor motorhome? Or is there a gizmo I'm not aware of fitted on these vans?

Thanks

I fully agree with you, I will be having double skinned tanks with a heating pipe going through the floor to both.
As I say easy to experiment with the heating on and test the temperature on trial runs.
Wonder what the fresh water temp is on the big A class vans with heated double floors. I think its worrying about nothing but would test mine anyway just to be sure.
Like you say the heating would only be on when its cold but need to be sure. I don't think the fresh water would get above 20 degrees for any significant period and is easy remedied if you have valves on the heating pipes.

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[CazPaul]

I did think about isolating the heating through that area, then figured the heating would only be on if it was cold anyway?

Surely this is the same on any twin floor motorhome? Or is there a gizmo I'm not aware of fitted on these vans?

Thanks

No gizmos that's why I think its worrying about nothing. When we emptied the waste tank on our Hymer the water was tepid and obviously between 20 and 38 degrees which are the danger temps. How many people have you heard of having a problem? None to my mind, we certainly didn't.
Our fresh tanks on the 2 Hymers were inside although I never tested the temps.

 

[bigtwin]

I know I must be missing something very simple, but I can't see what it is.

Please someone, what am I missing? It's driving me nuts.

Quite possibly that those that gave you the benefit of their ‘wisdom’, know less about the issue than you do?

One of the problems with fora is that without knowing the background /knowledge /qualifications of those providing answers to questions, it can be difficult to understand whether responses are just opinions or whether it is knowledge/facts. There are many around willing to offer opinions.

If I’m offered recommendations for restaurants from someone that I know likes, for example, KFC/Toby Carveries, I will listen politely but know that I’m unlikely to act on their recommendations.

Ian

 

[Lenny HB]

What you are suggesting is what most German manufacturers do.
Even with the double floor Hymers have GRP box that goes right through the floor it is insulated with pu foam and has an air gap around the tank. Heat is fed from the blow air heating with a 30mm dia duct fed of the main system.

 

[Wissel]

Thanks guys. Just questioning myself when I was told I was wrong.

Thought it best to check with others I'd prefer to look an idiot than get it wrong

 

[pyro]

This is just a guess (I claim no expertise in the matter):

From: http://www.hse.gov.uk/healthservices/legionella.htm

"Legionella bacteria is commonly found in water. The bacteria multiply where temperatures are between 20-45°C and nutrients are available. The bacteria are dormant below 20°C and do not survive above 60°C.

Legionnaires’ disease is a potentially fatal type of pneumonia, contracted by inhaling airborne water droplets containing viable Legionella bacteria. Such droplets can be created, for example, by: hot and cold water outlets; atomisers; wet air conditioning plant; and whirlpool or hydrotherapy baths"

In other words, droplet distribution, you inhale the water droplets (as you could by water being pumped through a sink tap & splattering) and you do not have to drink it to be at risk

From the same site: "Cold water should be stored and distributed below 20°C"

The fact that someone has done it and not had a problem seems a curious basis on which to discount a well documented risk.

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[two]

Don't forget that you only need to keep the water above 0°C. Even though my underfloor and garage get 'very warm' (I've not measured it, but the garage can get 'cosy' in winter and wine underfloor has become warm rather than stay cold) I don't think the water gets as warm (it doesn't feel warm out of the tap). If there was a problem, I think we'd have heard about it as lots of vans are built like that. Good to have thought about it, though.

 

[peterc10]

This is just a guess (I claim no expertise in the matter):

From: http://www.hse.gov.uk/healthservices/legionella.htm

"Legionella bacteria is commonly found in water. The bacteria multiply where temperatures are between 20-45°C and nutrients are available. The bacteria are dormant below 20°C and do not survive above 60°C.

Legionnaires’ disease is a potentially fatal type of pneumonia, contracted by inhaling airborne water droplets containing viable Legionella bacteria. Such droplets can be created, for example, by: hot and cold water outlets; atomisers; wet air conditioning plant; and whirlpool or hydrotherapy baths"

In other words, droplet distribution, you inhale the water droplets (as you could by water being pumped through a sink tap & splattering) and you do not have to drink it to be at risk

From the same site: "Cold water should be stored and distributed below 20°C"

The fact that someone has done it and not had a problem seems a curious basis on which to discount a well documented risk.

As @Lenny HB says, same with my Hymer, except I have the Alde heating. All carefully designed to keep the tanks from freezing in the winter when you have the heating on. Certainly nowhere near enough heat to warm all that water up to anything like 20C. And in the summer we don't have the heating on.

But in the summer in warmer climes the temperature in all our mohos will reach much greater than 20C. All you with tanks actually in the moho must be sh*****g yourselves now eh? And all those caravanners with those aquarolls out in the sun. OMG ..............

 

[joka250]

This is just a guess (I claim no expertise in the matter):

From: http://www.hse.gov.uk/healthservices/legionella.htm

"Legionella bacteria is commonly found in water. The bacteria multiply where temperatures are between 20-45°C and nutrients are available. The bacteria are dormant below 20°C and do not survive above 60°C.

Legionnaires’ disease is a potentially fatal type of pneumonia, contracted by inhaling airborne water droplets containing viable Legionella bacteria. Such droplets can be created, for example, by: hot and cold water outlets; atomisers; wet air conditioning plant; and whirlpool or hydrotherapy baths"

In other words, droplet distribution, you inhale the water droplets (as you could by water being pumped through a sink tap & splattering) and you do not have to drink it to be at risk

From the same site: "Cold water should be stored and distributed below 20°C"

The fact that someone has done it and not had a problem seems a curious basis on which to discount a well documented risk.

Having suffered respiratory problems from inhalation of contaminated water droplets I was assured by HSE that consuming the infected water was not in itself a problem. My assumption therefore is that the most likely problem will be caused by showering and accidentally inhaling toxic droplets. Drinking the water not a problem except for taste.

 

[EssexBoy]

If it helps, my Laika van is exactly as you're planning.
The heating keeps the water from freezing, but certainly doesn't heat it up. Its still bloody cold...
I suspect the blown air in the van just wouldn't have the oomph to actually get the temperature of the water too high.

 

[Robert Clark]

I do

A anti bacterial decent water filter such as E2 by 3m would save the expense and hassle of carrying bottled water

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[bigtwin]

But in the summer in warmer climes the temperature in all our mohos will reach much greater than 20C. All you with tanks actually in the moho must be sh*****g yourselves now eh? And all those caravanners with those aquarolls out in the sun. OMG ..............

No, they are well insulated from the external temperature - the water from our taps is lovely and cool. But I would worry for those with their uninsulated underslung tanks. OMG .......

Ian

 

[jtp890]

Previous van was winterised Dethleffs. Water tank was under dinette seat grey waste underslung and sprayed with foam.
Never had a problem to _ 10

 

[Eddystone]

Having suffered respiratory problems from inhalation of contaminated water droplets I was assured by HSE that consuming the infected water was not in itself a problem. My assumption therefore is that the most likely problem will be caused by showering and accidentally inhaling toxic droplets. Drinking the water not a problem except for taste.

This is an interesting point.
We have had a caravan for 40 yrs and have underslung water tanks on our Moho and have never considered there may be a problem.

 

[BusyBuilder]

What you are suggesting is what most German manufacturers do.
Even with the double floor Hymers have GRP box that goes right through the floor it is insulated with pu foam and has an air gap around the tank. Heat is fed from the blow air heating with a 30mm dia duct fed of the main system.

We have a pull string to divert heat into and around these areas to stop freezing but I would think it'll have to be very cold.

 

[Wissel]

We have a pull string to divert heat into and around these areas to stop freezing but I would think it'll have to be very cold.

I love Winter sports, plus we are both keen photographers. A long trip around Sweden and Norway is on the cards, plus we want to spend at least 6 months in Iceland, down the line.

Just trying to make the van as adaptable to different conditions as possible.

Thanks.

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[joka250]

This is an interesting point.
We have had a caravan for 40 yrs and have underslung water tanks on our Moho and have never considered there may be a problem.

I think it's quite probable that with regular use and sensible practice of draining and flushing tank at least at end and start of season the likelihood of a problem is kept to a minimum. As other posts mention there needs to be some element of temperature in the stored water somewhere from 20 deg up to 40 ish. Our tank heater only holds the water a little above freezing and cuts out at 5 or 6 deg. The problem is likely to be if continually warmed over longer periods and perhaps too well insulated. 20 degrees is not particularly hot after all .

 

[two]

I love Winter sports, plus we are both keen photographers. A long trip around Sweden and Norway is on the cards, plus we want to spend at least 6 months in Iceland, down the line.

... so you won't be needing a compressor fridge there!

 

[CazPaul]

I think it's quite probable that with regular use and sensible practice of draining and flushing tank at least at end and start of season the likelihood of a problem is kept to a minimum. As other posts mention there needs to be some element of temperature in the stored water somewhere from 20 deg up to 40 ish. Our tank heater only holds the water a little above freezing and cuts out at 5 or 6 deg. The problem is likely to be if continually warmed over longer periods and perhaps too well insulated. 20 degrees is not particularly hot after all .

Yes but 20 degrees is too hot for the fresh tank, that s the important part the fresh. It needs to be below 20 to be safe.
Hot water fine if you turn the boiler to 60 degrees once a week at least, its the cold that needs to be watched.
I cant see a problem at all really with heating an external box around the fresh tank. It will be well below 20 degrees I think.

 

[joka250]

Yes but 20 degrees is too hot for the fresh tank, that s the important part the fresh. It needs to be below 20 to be safe.
Hot water fine if you turn the boiler to 60 degrees once a week at least, its the cold that needs to be watched.
I cant see a problem at all really with heating an external box around the fresh tank. It will be well below 20 degrees I think.

As previous posts have said that's fine until you sit in temperatures of 30+degree with an over insulated tank and the water temperature can reach 20 or more. I have just heated some water to 25 degrees and to my feel it's not that hot. Also while I would advocate and support your advice to run boiler to 60 degrees my understanding is that that alone will not kill legionella bacteria. Also legionella is not the only bacteria created in water, my particular problem was caused by water borne bacteria that thrived at 5 degrees. All this is slightly academic for most of us but I feel it would be easy to over do the task of avoiding freezing.
With an underslung tank, no insulation thermostatic tank heater off grid and just 2 120amp batteries we survived 5 days of minus 10 overnight and daytime highs of minus2 last winter.

 

[CazPaul]

As previous posts have said that's fine until you sit in temperatures of 30+degree with an over insulated tank and the water temperature can reach 20 or more. I have just heated some water to 25 degrees and to my feel it's not that hot. Also while I would advocate and support your advice to run boiler to 60 degrees my understanding is that that alone will not kill legionella bacteria. Also legionella is not the only bacteria created in water, my particular problem was caused by water borne bacteria that thrived at 5 degrees. All this is slightly academic for most of us but I feel it would be easy to over do the task of avoiding freezing.
With an underslung tank, no insulation thermostatic tank heater off grid and just 2 120amp batteries we survived 5 days of minus 10 overnight and daytime highs of minus2 last winter.

You are talking about summer temps, if there was an issue then this would affect loads of motorhomes in summer so don't think there is anything to worry about.
The OP is talking severe cold winter use and how to stop the tank freezing solid.

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