Advice on moving unvented cylinder

Discussion in 'Plumbers' Talk' started by The_Doc, Mar 26, 2021.

  1. The_Doc

    The_Doc Member

    Hi All,

    I have just come up with an idea and wanted some advice. I need to move my CWS tank from the middle of the loft in order to convert it and also whilst i'm at it I would like to move the cylinder from the airing cupboard in order to enlarge my tiny bathroom.

    So current setup

    CWST in loft with vented cylinder in airing cupboard. The water is heated by immersion (no gas). Shower is pumped (absolutely amazing) and I have a bath (will be removed), a bathroom sink and a kitchen sink.

    My initial plan was to get an unvented system in the cupboard under the stairs on the ground floor, however I cannot do that myself and it just seems impossible to get anyone to come and quote, let alone do the work! Also I just prefer to do things myself as I know they will be done right and exactly how I want it done.

    However, now I have the plans finalised for the conversion there's room for a coffin style CWST behind the ashlar walls, so I was wondering if I could install the hot water cylinder in the cupboard on the ground floor?
    I'm assuming the head pressure will be pretty much the same as the tank is still in the loft, but i cant say I have ever seen this before?

    All I really care about is the shower, which is pumped (yeah might need a different pump as height will be greater) soas long as something comes out the other two taps then I'm happy.

    This will give me the space I require, I can do it myself, will cost a few hundred quid and I wont have an annual service so I'm struggling to see a catch other than its not possible.

    I did once live in a flat where the header was directly above the cylinder in a kitchen cupboard, and although the flow to the hot taps was somewhat pedestrian, it still worked.

    Am I missing something obvious with this plan?

  2. andy48

    andy48 Screwfix Select

    1. You are talking about moving a vented cylinder, not an unvented one as your title suggests.
    2. The head of pressure of tank fed outlets is determined by the distance from the base of the CWSC to the outlet. So if you move the HWC from the 1st floor the the ground floor, the pressure at the HWC will increase, but that gain will be lost and be back to its original value by the time the water "climbs" again to the outlet.
    3. The pump for the shower needs to be at the base of the HWC, so it and its pipes would need to be moved. Don't forget the shower pump needs a dedicated feed from the CWSC and a dedicated feed from the HWC via a special flange.
    4. You will need to run the vent pipe from the HWC up through the house to terminate over the CWSC.
    5. It's not a trivial amount of work, and need to be done right if you aren't to have future problems.
  3. The_Doc

    The_Doc Member

    Thanks for the reply, so it sounds like it's a plan then. Work not a problem, a weekend should have it sorted. Mistake in title, not sure how to change, not obvious on phone.

  4. rogerk101

    rogerk101 Screwfix Select

    Why don't you just remove the cold water storage tank and convert the whole house (hot and cold) to mains pressure?
    You'd have to change the hot water tank to being unvented (or you could do what I did, which is to put in a 12kW instant hot water heater).
    You could then flog your shower pump on eBay.
    The hot and cold systems would then be balanced, as they're both at mains pressure, the space savings are enormous, the efficiencies are huge, and you'd basically be bringing yourself into the 21st century and live like the other 90% of the developed world.
  5. The_Doc

    The_Doc Member

    Like I said, I want to go unvented but after 6 weeks of trying to get plumbers to come and quote I've given up. I must have contacted 20 local plumbers, the two that have bothered to pick up the phone or call me back have now cancelled 7 visits between them to come look and quote. So quite frankly sod them. It was my mate who said just keep unvented and move the tank downstairs, I had never thought of that, i'll have plenty of room in the eaves for a coffin CWST and I can do it myself. So today I have ordered/collected everything I need to move tank and refurbish bathroom including extending into airing cupboard for 1700 quid, (cylinder, new 3 bar pump, piping, shower enclosure, monsoon shower, sink, tiles, GU10 lighting, door, doorframe, plaster, breezeblocks, cement...) less than the labour would probably cost for the UV cylinder.

    I did seriously consider the 12kw instant heater but I was just worried it will be gash supplying all of the house, a few years ago i installed a 10.8KW shower at my parents when renovated their bathroom and its fairly average, especially in the winter, so i thought powering the entire house on one might be a bit rubbish. Plus it would put me very close to 80A on my supply as I have a fully electric house, so 6kw of heating if its all on at the same time.
  6. The_Doc

    The_Doc Member

    So after a month or so the tank is relocated into the cupboard downstairs, bathroom knocked through to airing cupboard, an awesome shower is installed and immersion is connected to my smart home system. The soldering is like me, ugly but strong but nothing so much as a week at any of the 50 odd joints I soldered so pretty happy with that. Just the rest of the tiling to finish and then ceiling and lights.

    [​IMG] [​IMG] [​IMG] [​IMG] [​IMG] [​IMG] [​IMG] [​IMG] [​IMG] [​IMG] [​IMG] [​IMG] [​IMG] [​IMG] [​IMG] [​IMG] [​IMG] [​IMG]
  7. rogerk101

    rogerk101 Screwfix Select

    Looks good. However I would not have used those plastic L couplings under the shower tray. No need for them at all, and they're a problem waiting to occur. There is more than enough flexibility in the plastic pipe not to have needed them. You could and should have just used some gentle curves. Good luck, and hold thumbs they all survive.
  8. The_Doc

    The_Doc Member

    I initially did them with straight couplings and curves but I wasn't happy with the amount of tension on the straight coupler, so went with the 90 degrees. Why its it a problem waiting to happen? There are millions upon millions of these connectors out there, so I don't sign up to plastic fitting paranoia.
  9. rogerk101

    rogerk101 Screwfix Select

    The manufacturers' advice for them is not to use them in inaccessible places. I would consider being buried under a shower tray to be pretty inaccessible. Of course they are always accessible, but removing a shower tray is a tad more disruptive than removing a removeable bath panel.
  10. The_Doc

    The_Doc Member

    The shower tray is on riser legs so it is fairly accessible, if a little awkward. The legs being the main problem routing without the bends, which needed sharp curves to get between the legs and back to the wall.
    pppmacca43 likes this.
  11. FlyByNight

    FlyByNight Well-Known Member

    You could have gone for pipe formers which allow continuous runs with swept 90 degree bends. They work well.
  12. The_Doc

    The_Doc Member

    I could have done, but putting elbows in is even simpler!
  13. FlyByNight

    FlyByNight Well-Known Member

    Is it? Pipe formers take 10 seconds to fit, no measuring to length, no cutting, no checking insertion depth, no hidden joint.
  14. pppmacca43

    pppmacca43 Active Member

    As long as you have fitted them properly, with nice clean cuts and inserts, they’ll be fine.
    If they aren’t it’s because u have been very unlucky.
    The majority of new houses in the country for the last 10/20 years are fitted with pushfit in walls and floors so I don’t think putting a couple under a removable shower access panel is too bad :)
    BiancoTheGiraffe likes this.
  15. The_Doc

    The_Doc Member

    The bag of elbows was in my hand, getting formers would have meant a trip to Screwfix for the 378th time that day!

    Look this was the best solution. I originally planned to do it in copper but when I got the boards up the wall where the shower feeds are is sat on an RSJ so I couldn't go straight down. Plus I was buggered by other pipes in the way to both in the feeds, so I felt this was the best and easiest solution.
  16. The_Doc

    The_Doc Member

    Indeed, my partner's house built in 2013 is totally plumbed with them, and without as much pipe support as I would put in!

    Pipe was cut with shears, inserts used, pushed home into fittings. If they let go then either I've screwed up or very unlucky.

    What would they think if I capped off the no longer needed bath feed from the CWST with a speedfit stopend....
    pppmacca43 likes this.
  17. BillyBobToo

    BillyBobToo Active Member

    There shouldn't be an isolator on the open vent outlet of the cylinder.

  18. The_Doc

    The_Doc Member

    I put isolators everywhere, probably shouldn't have put one there but hey ho, its in now.
  19. BiancoTheGiraffe

    BiancoTheGiraffe Screwfix Select


    I'm amazed by how many I'm finding in walls and underfloors at my new place (2000 build).
  20. pppmacca43

    pppmacca43 Active Member

    Yep, normally find elbows in the walls with copper poking out behind pedestal basins etc, always a worry when u don’t know it’s plastic behind lol and the copper is spinning

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