Discuss Hot water tank question. in the Plumbing Forum | Plumbing Advice area at PlumbersForums.net

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giveitago

Hello everyone. I am looking for a bit of basic advice on hot water tanks. I currently have a warm air heater that heats up the water in my tank via a heat exchanger. The tank is now very old and does need sorting out. I am getting a brand new, unvented tank as a replacement, with an immersion heater included for back up purposes. I don't really know much more than the basics about this subject though.

I wondered if there is much of a difference in the quality of tanks available on the market? I obviously want to get something that is very good quality and will last a very long time. I would far rather tell my installer what to get me, than leave it all down to him. Not that would I expect to get junk, but I am sure everyone can appreciate where I am coming from here. Any other tips or advice would also be greatly appreciated. For example, are there any special features I should know about? Thank you.
 
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AMGasServices

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If you’re going for unvented make sure the chap you use has G3 tickets, checks water pressure, also a drain for the PRV.

I’d say go with a vaillant unistore.
 

Jim Goodenough

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There's many makes on the market. Make sure whatever you choose has a 25 yr guarantee, which most of them do. Stainless steel is much more durable than glass-lined steel.
 

Jim Goodenough

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If you’re going for unvented make sure the chap you use has G3 tickets, checks water pressure, also a drain for the PRV.
As AMGasServices says must be G3 certified, check flow rate as well as pressure, really need 22mm mains to UVHWS Cylinder so you need to check size of incoming mains.
 
OP
G

giveitago

Thank you very much for all of the replies. Unless I am looking in the wrong places, then the Vaillant Unistor seems to be the cheapest option, which does admittedly suit me best. :-0 Have I got that bit right? Also, does the Vaillant Unistor have any obvious drawbacks over a comparable Gledhill or Heatrae Sadia model? Thanks again for the help.
 

AMGasServices

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I think their pretty much the same but see jims advice below.

Also you will need an indirect unvented cylinder because it will have a coil inside it to heat the hot water via your warm air unit.

Direct unvented cylinder only run on immersion.

There's many makes on the market. Make sure whatever you choose has a 25 yr guarantee, which most of them do. Stainless steel is much more durable than glass-lined steel.
 
OP
G

giveitago

I take it that an indirect, unvented cylinder would use the very same coil for immersion heating purposes? After it was wired up properly of course. Or would a new coil have to be added to the tank? Thank you.
 

Last Plumber

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Vaillant Unistor is the one I would personally go for. Others mentioned above are very good though.
Your installer will have his/her own preferences though. If they are going to be looking after it from installation onward, it may be an idea to go with their advice.
 

AMGasServices

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Look at the picture the indirect cylinder has the coil inside it and a immersion as a backup.

They’re both separate but do the same job.

EEB62CED-EA43-4AFF-98A1-39C898100D14.jpeg
 
OP
G

giveitago

I have decided to mention the Vaillant Unistor to my installer to see what he thinks. It definitely seems to be a bit cheaper than the Heatrae Sadia Megaflo.

I see that the coil heated up via the boiler heat exchanger seems to be a lot bigger than the immersion element and is possibly made with a different metal. I still can't help but wonder whether future water tanks could somehow be designed so that this same coil could also double up as an immersion element. I hope I don't get lynch mobbed off the forum for saying stupid things. Ha ha.

One other thing. Our old boiler was a Johnson and Starley J25-32 MK2 warm air heater, a real trooper, which we replaced with a Johnson and Starley C10 DW and we are very happy with it by the way. Our hot water tank is the same one that was originally installed with our old boiler, when our block of flats was first built in the mid 1970's.

However, it is seemingly encased in a wooden box and we haven't got a clue what capacity it is. Is anyone able to hazard an educated guess for me? We were reasonably happy with the capacity of our old tank and want to get an idea of what sort of capacity we should be looking at for our replacement you see. Much appreciated.
 

Best

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You can specify an extra immersion element boss on the side of cylinder.
This would mean you have a lower element to heat entire cylinder and an upper element that will heat a smaller amount of water, or as an extra working element should you wish.
 

Ric2013

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I see that the coil heated up via the boiler heat exchanger seems to be a lot bigger than the immersion element and is possibly made with a different metal. I still can't help but wonder whether future water tanks could somehow be designed so that this same coil could also double up as an immersion element
No, just laughed at, though I would be genuinely interested in understanding what advantage you see in having them incorporated.

The immersion is an electrical heating element which is able to both generate heat created from electrical resistance, and then transfer its heat effectively over a small area from the heated metal element to the water. When the electrical element fails, the immersion heater is a cheap and easily (usually) replaceable part.

The large coil is a water to water heat exchanger, so does not have much similarity, and is not replaceable. It needs a much greater surface area for reasons that I do vaguely understand at the best of times, but not this close to bedtime :)

If your suggestion is to incorporate the immersion into the coil, I can't see much advantage. Perhaps the greater surface area means the surface temperature of the alternative-design coil would be lower and this would reduce limescale formation.

The other benefit of having them separate is that if you are in a massive hurry for hot water, you can run both the boiler and the immersion heater at the same time.
 
OP
G

giveitago

I bet you were straight off to the patent office, by candlelight, to secretly steal my great idea. :-0 What about finding out the capacity of my hot water tank then? Anyone have any ideas? Thank you.
 
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No point in patent office or a patent attorney - essex flange and its brother have been around for years and if this is even within a sniff no dice - I know thats what my company API 2006 do
 

Ric2013

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No point in patent office or a patent attorney - essex flange and its brother have been around for years and if this is even within a sniff no dice - I know thats what my company API 2006 do
I think he means patenting the idea of incorporating an immersion into the DHW coil. Trouble is it seems to be a misconception that you can patent an idea. I got to the patent office and was told I cannot simply patent an idea without a method of construction and ideally a working prototype as well as evidence that it was original and not something I pinched from some guy on a web forum :'(
 
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I have some current eu patents - working prototype is not nec. anybody can have a go but it costs and there are loads of tests/checks and can take years
 

Ric2013

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Heck. The lady at the patent office probably lied to me then. I bet she's patenting it herself now. (This, and my previous post, are a joke).
 
OP
G

giveitago

Ha ha. I think it's simply called banter. Theresa May is currently working on making it illegal, but we are all still safe for now.

It's a real shame it's impossible to figure out what capacity my old cylinder is, but never mind. I have finally decided to go with a 150 litre Vaillant Unistor standard, indirect, unvented hot water cylinder. I am confident that should be enough for us and I will make sure an immersion heater is fitted as a back up option.

Does anyone happen to know if any outlets sell these cylinders with an immersion heater already fitted? I would probably save a few quid that way. Thank you again to everyone who replied and I have learned a little bit.
 

Ric2013

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You can get an approximation of the capacity by taking the internal radius and multiplying it by itself, then multiply the result by 22/7, then multiply the result by the height.

Use inches as the measurement and then divide the result by 277.42 to convert from cubic inches to gallons. Or use cm and it gives the result in cc.
 
OP
G

giveitago

You can get an approximation of the capacity by taking the internal radius and multiplying it by itself, then multiply the result by 22/7, then multiply the result by the height.

Use inches as the measurement and then divide the result by 277.42 to convert from cubic inches to gallons. Or use cm and it gives the result in cc.
Did the lady from the patent office teach you that in bed? ;-) I did mention I had an old tank encased in a wooden box at the beginning of this thread, but, admittedly, I did then later mistakenly refer to an my old cylinder. My apologies. Unfortunately, it was impossible to access it and I eventually just guessed what size my new cylinder should be.

I got a ThermaQ Evocyl indirect 150 litre cylinder in the end, stainless steel and 25 year guarantee, which also came with an immersion heater backup option preinstalled. Does anyone have any rough idea what cost I should be looking at to get it wired up? Thank you.
 

ShaunCorbs

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Did the lady from the patent office teach you that in bed? ;-) I did mention I had an old tank encased in a wooden box at the beginning of this thread, but, admittedly, I did then later mistakenly refer to an my old cylinder. My apologies. Unfortunately, it was impossible to access it and I eventually just guessed what size my new cylinder should be.

I got a ThermaQ Evocyl indirect 150 litre cylinder in the end, stainless steel and 25 year guarantee, which also came with an immersion heater backup option preinstalled. Does anyone have any rough idea what cost I should be looking at to get it wired up? Thank you.
who plumbed it up?
 
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Your existing tank is probably an old Elson, Elsey & Gibbons rectangular copper tank. I used to sell loads of them back in the 1980's for bloaks of flats. From memory they were 85, 115 or 135 litre.
The ThermaQ is a good choice to replace it and the recovery from cold via the primary coil will only 25 minutes +.
As stated earlier it will have to be fitted by an engineer with a G3 ticket. They can be very dangerous if not fitted correctly.
 

AWheating

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I'm guessing the biggest issue will be the discharge as getting a separate waste to the stack may be impossible.
 
OP
G

giveitago

who plumbed it up?
The same guy who fitted my boiler. He had all of the necessary qualifications. He took away my old water tank without telling me what capacity it was though. I did ask him beforehand and he either forgot to check or just couldn't easily tell. All of the work on my boiler and water tank has now been fully completed.



Your existing tank is probably an old Elson, Elsey & Gibbons rectangular copper tank. I used to sell loads of them back in the 1980's for blocks of flats. From memory they were 85, 115 or 135 litre.

Thank you very much for the information. My new cylinder appears sooooooo much bigger, but looking at a cylinder, as opposed to a rectangular wooden case, can be so misleading when it comes to judging actual volume. I at least now know I am 15 litres better off, minimum, and might even be 35 litres better off. I seriously doubt my old water tank had as little volume as 85 litres.



I'm guessing the biggest issue will be the discharge as getting a separate waste to the stack may be impossible.
Do you mean the condensate pipe? If so, then I can't see anything running up to my roof alongside my new dual flue. However, I can see a small pipe coming out of my boiler and running sideways through my airing cupboard. I can't see where it runs from there though.

Does anyone have a rough idea what cost I should be looking at to get my immersion heater wired up then? The guy who installed my boiler and water tank said it was something he doesn't do. I want to get a vague idea in my head, before ringing someone up next week, and it certainly isn't the easiest thing to find out online. Thank you.
 
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