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Discuss Hot water tank question. in the Plumbing Forum area at UKPlumbersForums.co.uk.

  1. giveitago

    giveitago New Member

    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.
  2. Karl

    Karl Member

    Gledhill are decent
    • Dislike Dislike x 1
  3. AMGasServices

    AMGasServices GSR

    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.
  4. Jim Goodenough

    Jim Goodenough Plumber

    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.
    • Agree Agree x 1
  5. djchristoff

    djchristoff New Member

    Go for a Heatrae Sadia premier Plus which is all pre plumbed ready to fit.
  6. Jim Goodenough

    Jim Goodenough Plumber

    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.
  7. giveitago

    giveitago New Member

    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.
  8. AMGasServices

    AMGasServices GSR

    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.

  9. giveitago

    giveitago New Member

    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.
  10. Last Plumber

    Last Plumber Trusted Plumber GSR

    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.
  11. AMGasServices

    AMGasServices GSR

    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.

  12. Gasmk1

    Gasmk1 GSR

    isnt the vaillant made by gledhill anyway
  13. giveitago

    giveitago New Member

    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.
  14. Best

    Best Trusted Plumber

    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.
  15. Ric2013

    Ric2013 Plumber

    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.
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