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Do I need a hot water cylinder?

  • 12-03-2022 12:38pm
    Registered Users Posts: 789 ✭✭✭ fatbhoy

    I'm wondering if people could advise me regarding whether to get a hot water cylinder or not in my house.

    Currently, I've an old gas central heating boiler, probably '90s, that I don't plan to upgrade anytime soon. There's also an electric shower in the bathroom, installed in the bath. The bath also has one of those hose mounted shower heads connected up to the bath taps. Downstairs, in the living room cupboard, there's a really old copper hot water cylinder, and that either needs to be replaced or removed permanently to free up space.

    The way the house works at the moment is this: people use the electric shower to wash, and uses a kettle of hot water to shave with in the bathroom because there's no hot water. To wash the dishes in the kitchen, people boil water in the kettle and use that in the sink.

    I've hopefully a plumber coming to do a couple of jobs in the house soon (install a stop-water valve, and replace the toilet cistern syphon), and I'm wondering if I should bother getting him/her to replace the hot water cylinder: do I need it? would it mean hot water would be available in the sink in the bathroom and bath taps, and downstairs in the hot tap of the kitchen sink? I'm not sure how all this works, you see. I'd probably seldom use the cylinder, but I suppose it would be an addition to the house and a nice-to-have feature, which would also be of benefit if I was to sell the house.


  • Registered Users Posts: 9,405 ✭✭✭ antoinolachtnai

    You may not be planning on it but your boiler is going to need to be replaced in the next few years. It is unrealistic to expect a boiler to last more than 23 years.

    You could fit a combi boiler which would not need a cylinder but because you would need an extra pump to do this properly, there wouldn’t be much of a money saving.

    if you remove the cylinder from your present setup you will no longer have a facility for heating water for the taps you could install electric instant water heaters certainly but it would entail more expense

    It’s your house and you can do what you like but I wouldn’t leave the house without a means to heat water at the hot water taps if it were my house. If you are going to sell the house you will need this facility in place to get the full value.

  • Moderators, Science, Health & Environment Moderators Posts: 18,072 Mod ✭✭✭✭ Sam Russell

    A few issues you might consider.

    1. Are you in a hard water area? Hard water causes problems with hot water tanks.
    2. Is your hot water tank properly insulated? Using an electric kettle to heat water costs the same as using an immersion hot water system. Gas is much cheaper to heat water, so your boiler will heat the water for less if your tank is well insulated.
    3. A new condenser boiler is much more efficient. A combi boiler gives instant hot water, so you will not need a hw tank, but, probably, you will need a water pump, unless you have a strong water main pressure and flow.

    [By the way, I am not a plumber.]

  • Registered Users Posts: 789 ✭✭✭ fatbhoy

    Thanks for the replies.

    Hi  antoinolachtnai

    I guess it's confirming what I suspected, that it would be a good idea. What kind of price would it be to remove the old cylinder, install a new, insulation-coated one, and get it all working (e.g. the immersion switching gear probably needs to be upgraded too)? Would 1K cover it, or is that too much? I'm based in Dublin.

    Hi Sam Russell.

    1. Normal/soft water area. Drimnagh, Dublin.
    2. Nope. The existing one is like what I had in the '70s growing up: an old copper cylinder with a lagging jacket tied around it. It's all in tatters now. I'm pretty sure none of it works: I bought the house about 8 years ago and I was afraid to switch it on so I assumed it didn't work. When I first moved in a plumber, who was doing another small job, took a quick look and said it was fucked and needed replacing, although I can't remember the details of what he said, or what checks he did. I'll have a poke around it over this weekend. I've a plumber coming in a few days time to do a bit of other work in the house and also to look at this cylinder and quote on replacement etc..
    3. Yeah I'll probably get a new boiler over the next 5 years or so. Water pressure from the mains is pretty strong here. I'll see what the plumber who's coming says.

  • Registered Users Posts: 178 ✭✭ headtheball14

    I'm thinking of removing the HW tank entirely to free space and replace with a couple of water heaters . You can get them in Screwfix for a couple of hundred quid. Would work better with use in house, I don't need a tank often , and when I do the water has cooled down so much we boil the kettle anyway .saying that o don't have gas. Combi boiler best if you have gas

  • Registered Users Posts: 9,405 ✭✭✭ antoinolachtnai

    Re your questions 1000 euros should do it if you can find anybody to do it. You might be better off to save your money or borrow some more to do the whole job though, and replace the boiler at the same time. The larger job will be more attractive for a plumber to take on. The boiler is going to fail anyway and the rising cost of gas makes it attractive to get a more efficient boiler. Put in thermostatic radiator valves at the same time. It’s a bit of an investment but will be worth it for long term. If it were me I would put in a pumped shower connected to the cylinder. It’s a good improvement in comfort and If your electric shower is more than seven years old and is being used daily it will also need replacement soon in any case

    To do a proper job with a combi you need a pump whether you have good pressure or not. Otherwise you’re not meeting the required spec.

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  • Registered Users Posts: 789 ✭✭✭ fatbhoy

    If it were me I would put in a pumped shower connected to the cylinder. It’s a good improvement in comfort and If your electric shower is more than seven years old and is being used daily it will also need replacement soon in any case.

    Do you mean get rid of the electric shower and put in the water cylinder with some sort of pump attached to it? If so, could I just get the new cylinder, and later on down the line get the pump thing?

  • Registered Users Posts: 3,004 ✭✭✭ phormium

    I'm no expert but just a question as I'm puzzled, why is there no hot water in any of the taps?

    I have what sounds like similar set up, 30 yr old gas boiler, tank in hotpress (had to replace mine few years back when it sprunk a leak but replaced with same but with the insulation around it, which I might add does not keep the water as hot as the diy set up I had with the old one of old duvets tied around it!). Anyway once my boiler has been on to heat rads the tank will also be warm so it powers a shower (also have an electric one) and water to all the hot taps, the temp of the water depends on how high I had the boiler on.

    I also have an immersion in the tank which I can turn on in summer for example when the heat won't have been on, 5 mins will give me roasting water to wash dishes for example. I know on my control thingy it looks like I have an option to turn on just water heating as opposed to rads but I don't actually, it only works one way and if you turn on the boiler then both rads and water heat unless of course you turn off the rads. Maybe yours does actually have an option and what you are saying is you only ever use the heat option and not the water because of the state of the tank?

  • Registered Users Posts: 9,405 ✭✭✭ antoinolachtnai

    Yes you could get the pumped shower later. I suggest you do it in one go though. It will be less expensive overall. Also at a time when it is hard to get plumbers the larger job will be more attractive to quote on

    you could also go with the combi option. But I really advise you to get enough plumbing/heating work done in one go so you don’t need to mess around with it again for another 20 years.

  • Registered Users Posts: 34 WillContribute

    If you can consider a combi boiler, seriously consider it. It will give you instant hot water. The combi boiler is only about 100 euro extra(wholesale) than a standard one (heating only) and it's a few pipes extra for the plumber and some capping off. Just small amount of extra work when changing the boiler anyway. You do need to check your mains pressure/flow. You need min 12l/min. The more the better Just open the kitchen tap fully and time to fill up a 2l milk carton. Then calculate how many cartons you can fill in a minute. If the flow is over 12l/min (6 cartons) you don't need an extra pump. You would be able to comfortably run the sinks/kitchen taps and also a new thermostatic shower valve off the mains cold and hot (via boiler). First thing check your flow rate!

  • Registered Users Posts: 789 ✭✭✭ fatbhoy

    Just glancing at the replies now, but I'll revisit later when I've time.

    I'm not really sure about the boiler thing because we seldom use the central heating. We probably only use it for an hour or two a day if the temperature outside is less than 5 - 7 degrees. Otherwise we layer-up. We're saving the planet 🤣

    The existing gas boiler is outside in a little brick shed outside the kitchen back door. With this is mind, I wonder would it be good to upgrade it to combi? The answer is probably yes, since it will (apparently) need upgrading soon (I think it's a 70% efficiency one: a Potterton Prima), and a combi seems to be only about 10% more expensive than an ordinary one, at least for the hardware itself.

    Anyway, thanks for the replies: I wasn't expecting so many with so much useful information; hopefully it will help other people reading this thread as well as me.

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  • Registered Users Posts: 213 ✭✭ Bellie1

    Hijacking thread. Wonsidering replacing current 18 year old gas boiler with combi. Pipes in house must be almost 40 years old so not sure if worth the risk of leaks ? We rarely need hot water so considering getting regular boiler with heat controls so can just have permanently set to rads only ..No hot water but we'll live without ( can boil kettle for washing dishes).