[tlwcs]

Any physicists on here please?
350 wyvale tank with 3kw element in the bottom, correctly fitted and 16amp wired
Tank filled to 2 inches from the top and set for 8 hours heating
The top of the tank is imploding
I’ve drilled a little hole in the black filler cap, to complement the one in the vent cap (spring loaded one)
I even left the lid off the night and struggled to re fit it the next morning
The only thing  I can think is the waters getting too hot.  (Where’s Nathon?)
Any ideas please chaps
Tony

[Ched]

So if tap water is about 7degC in winter and you have 3Kw heater for 8 hrs then the 350litre tank should have reached about 65degC assuming zero losses.
What temp do you have the immersion heater thermostat set to?
When you heat water it expands so having the top of your tank implode seems weird.
How is your tank mounted? IS it bolted in frame or a strapped down tank?
It could be that the sides are bowing pulling down the top of the tank unless a frame is there to stop the sides bowing?

[tlwcs]

So if tap water is about 7degC in winter and you have 3Kw heater for 8 hrs then the 350litre tank should have reached about 65degC assuming zero losses.
What temp do you have the immersion heater thermostat set to?
When you heat water it expands so having the top of your tank implode seems weird.
How is your tank mounted? IS it bolted in frame or a strapped down tank?
It could be that the sides are bowing pulling down the top of the tank unless a frame is there to stop the sides bowing?

Thanks Ched.
Thermostat set to max
Tank not insulated, keeps windscreen clear.
Tank in a frame but only strapped in.
I left it off last night so it’s relaxed back a little

[Smudger]

Hmm.. good point ched - interesting g problem

Darran

[Pete Thompson]

It’s not imploding exactly.

The heated water is making the tank plastic softer and then the weight of the water is constantly pushing on the sides, making them bow outward. (Imagine if you put water into a plastic bag, then placed it on a flat surface. It will tend to spread out flat).

This distortion has the effect of pulling the top of the tank inwards.

I have noticed the same very slight effect on my tank, but as it has a steel frame surrounding it, it’s just a very slight bulge in the lowest 3rd.

[NWH]

As the water vapour cools it condenses into liquid water,this lowers the internal pressure and can cause it to collapse and it’s one reason I wouldn’t go down this route.

[NWH]

Again speak to a plumber I haven’t seen many fitting plastic tanks in airing cupboards lately.

[NWH]

It’s not imploding exactly.

The heated water is making the tank plastic softer and then the weight of the water is constantly pushing on the sides, making them bow outward. (Imagine if you put water into a plastic bag, then placed it on a flat surface. It will tend to spread out flat).

This distortion has the effect of pulling the top of the tank inwards.

I have noticed the same very slight effect on my tank, but as it has a steel frame surrounding it, it’s just a very slight bulge in the lowest 3rd.

It’s not imploding completely but it’s on its way to doing so.

[Ched]

Just so you know Wydale tanks are made of Medium density polyethylene. Medium and high-density polyethylene has a melting point is typically in the range 120 to 130 °C.
So while a immersion heater wont get the pure upto anywhere near 120degC it may cause the tank to go a bit soft, certainly soft close to element if no circulation.

[G Griffin]

As the water vapour cools it condenses into liquid water,this lowers the internal pressure and can cause it to collapse and it’s one reason I wouldn’t go down this route.

Would lower pressure cause it to collapse?

[KS Cleaning]

Again speak to a plumber I haven’t seen many fitting plastic tanks in airing cupboards lately.

Alternatively, just login to CIU and ask the resident expert on all things hot, NWH 🤣🤣🤣🤣

[NWH]

🤣🤣😘

[Pete Thompson]

As the water vapour cools it condenses into liquid water,this lowers the internal pressure and can cause it to collapse and it’s one reason I wouldn’t go down this route.

How would that be possible when he’s drilled a hole in the lid? The “internal pressure” would equalise to the external pressure.

[NWH]

When he’s heating the water he is creating steam which turns into water vapour eventually if the blow off valve or hole in the lid isn’t big enough “boom”,how big is the air hole.

[NWH]

You would be better off putting 2 vents in either end of the tank you could use a threading tool for 2 female John Guest fittings,I’d use 3/8” or in English 1/2” and stick 6” long pipe in both.

[AuRavelling79]

I use an immersion and personally I think 50 degrees c is as high as I would go in the tank. If you want hotter then go diesel.

[֍Winp®oClean֍]

As the water vapour cools it condenses into liquid water,this lowers the internal pressure and can cause it to collapse and it’s one reason I wouldn’t go down this route.

Utter nonsense, the tank is vented you berk!🤔😆

[Smudger]

When he’s heating the water he is creating steam which turns into water vapour eventually if the blow off valve or hole in the lid isn’t big enough “boom”,how big is the air hole.

Steam ? - he's not boiling a kettle - if he was that would put your all singing a dancing system to shame wouldn't it.....

Darran

[NWH]

When that water is heating up in the tank it’s causing vapour or condensation if it’s not it would be a completely open lid even then there would be some steam after time,people are heating these tanks and insulating them during that process not only static in vans as well all that heat and steam will create pressure if you have a tiny little hole in the tank,matter of time before the tank folds in on itself.

[G Griffin]

When that water is heating up in the tank it’s causing vapour or condensation if it’s not it would be a completely open lid even then there would be some steam after time,people are heating these tanks and insulating them during that process not only static in vans as well all that heat and steam will create pressure if you have a tiny little hole in the tank,matter of time before the tank folds in on itself.

The tank isn't insulated.
Steam would create outward pressure and blow, as you said, but is it getting hot enough to create steam? I know Nathan did  get a bit of steam but it didn't blow. Then again, we haven't heard from him for a while  .
Steam could cause outward pressure, the tank could expand and then contract as it cools and that could cause it to sag.
I think it would be depend on the water temperature and composition of the tank.

I've just re-read the first line the thread, so ignore all that ^^^  .