How does a hot water tank work?

[WhatsitWiggle]

I've lived in my house for 15 years, always using gas boiler to heat hot water for 2 hours in the morning and 2 in the evening.

But with fuel prices rising and me now being a single parent, it's made me question if this is necessary? I have a daily morning shower (4 minutes most days, 10 minutes twice a week to wash hair), washing up done every evening. Washing machine is a cold water fill. Every other week, DD stays with me - she takes longer showers or baths in the evening.

If I put the hot water on for 1 hour in the morning, is that enough to heat water for my shower? And will the hot water stay hot until the evening or do I still need to put it on again? If the hot water is set to come on again in the evening, but there's still hot water in the tank, does anything happen? Ie am I using gas or not?

With hindsight, I wish I'd changed to a combi boiler when the old one went kapput two years ago, but at the time a straight replacement was the quickest and cheapest option.

My tank’s thermostat is at 50c and it’s fine.
I have a shower before the boiler comes on in the morning, and it’s still warm from the night before.

it seems the timings can't be different for heating and hot water (I'd need a different timer at approx £70 plus fitting)

How does that work in summer - you have to have the heating on to have hot water?? I'd die of heat 😅

If you do think of changing, mine's a Honeywell ST9400C. It does heating and water separately and you cam have them on a three different times per day (each). And it's a 7 day programme so the times can be different every day of the week (eg, my weekend timings are different to my weekday ones). Price varies but I can see one on Ebay for £50.

Yes there are various models and the one we've got is pretty basic. I don't recall being given an option when it was installed either, I'd certainly have paid more to get more control. Tiresome is spot on!

@DisplayPurposesOnly no it's not that bad 😆 you can set hot water and heat separately to on / off / timed. So heat is currently off and hot water is timed. But I can't set different times for heating and hot water. They do make a version for that, and also with the option of different times for each day. As a short term, with the heating off I can set the timings just for the hot water and see how much I can save. And then calculate whether there's a benefit to changing the timer vs cost.

Feeling left out now, here is my beast if a water tank. I believe the top half deals with water and the lower bit heating. I liken it to a WWII bomb!

Are in Ireland? The dark green is not common in UK. The cylinder shape is also unusual, though it might be a combination cylinder.

The lower part has two immersion heaters so I think is for hot water, perhaps you have a cheap off-peak period for electricity. You have an additional circulating pump to the right. Do you have a wood stove? Or a bathroom distant from the cylinder? The arrangement is unfamiliar to me. It might be a thermal store. Do you get high pressure from the hot taps?

It looks rather like a Gledhill Torrent, but has more attachments.

@PigletJohn no, I am in England. We do not have a wood stove but do have a Rayburn. The bathroom isn't especially close (other side of the house and downstairs) but it's not a huge house, it's a four bed cottage. I think the hot water pressure is good, yes.

It was a nightmare when we moved in trying to figure it out. We don't get more than luke warm water when the heating is first turned on either because I gather the drain on it is too big, so have to remember not to try and run a bath if the heating has gone on in the last half hour!

It sheds loads of heat into the airing cupboard too. That bedroom is unusable in summer. Not sure whether insulating the pipes would make a lot of difference but I imagine that is where the loss is from. I don't think the people living here ever intended to move, I gather it wasn't cheap equipment to install either.

Oooh you are right I found a label!

I'm not familiar with that one, but I believe that the boiler (or immersion heater, at enormous cost) heats up a quantity of water, and the pipes to the hot taps run through it (the water does not mix) and become heated when you run a tap. This enables you to run high pressure water off the mains into the hot water pipes, which can give a powerful shower. I think you have large bore pipes to enable high flow. Yours probably slowly stores heat from the Raeburn, ready to be used when required. It may take a long time to heat up. You could also use solar if you have it.

See if you can find a local plumber experienced on them. Your Raeburn person, or a neighbour with something similar should know. The makers may keep a register of approved installers. Best to find someone before you need them.

Yes, lag the pipes. They are probably 22mm diameter (15mm are also used, and from the Raeburn, they might be 28mm, which is not widely stocked). The "Byelaws" grade is a thicker and better insulated, necessary outdoors or in unheated spaces, get a trial piece and see if it will fit (your pipes may be too close together.) You can cut and mitre it with a bread knife and bind joints with matching tape, or vinyl tape. The good stuff is fairly stiff and hard, like pool noodles, not squashy. Avoid cheap foam stuff (you will learn to recognise it by the feel). If you can get the engineer to identify what each pipe and valve does, write in on a sticky or tie-on label with a Stabilo marker. One day you will be glad you did. Also ask her to empty the Magnaclean and teach you how to do it. Once a year should be enough.

Examples:
www.wickes.co.uk/search?text=Lagging

The hessian bandage is not a good insulator, but it is still used to wrap round pipes to stop them knocking or scraping against joists or walls as they expand or contract. The pipes slide silently against it.

P.S.

When people realise how expensive heating will be this year, there will be a world-wide rush on insulation and lagging. So buy yours first.

Hi Piglet John, mine is like the blue one in the photo on p1 of thread but is light green.

We have a pump for the shower and have a gas aga.

Is there anything that I should do to reduce energy use (aside from removing aga - are looking into that!) - the cylinder thermostat is set to 65 degrees. We have water on for 1 hr per day. Heating hasn’t been on this autumn yet, but will be on no doubt from Nov and we tend to have 1 hr in morning and 5 hrs in evening with thermostat set to 18 degrees and room radiators set to different temps.

Thanks so much.

Green is older than the blue one. As a rule of thumb, the newer they are, the better the insulation, and the faster they heat up. I lose track but the green is probably 20 years old. Blue is current standard.

Is your cylinder being heated by the gas Aga? Or with an electric immersion heater?

It will help to insulate all the hot pipes, and there will be a slight saving from adding a red jacket over the green foam, if you can find one. Very few are sold now as most people already have insulated cylinders.

The pipe lagging is made of stiff plastic foam, I think it's foamed polythene. There are black synthetic rubber ones for outdoor and underground use. Pipes in an unheated space such as a loft or shed may freeze and need the "bylaws" grade which is thicker and better, I use it indoors as well if there is room (it is thick). You can cut and mitre it with a breadknife. Tape the joints. As soon as the cold weather comes, the shops will be stripped bare. Your pipes are probably 15mm and 22mm diameter, measure them for size. Old and large homes may have 28mm, harder to find. There are some cheap flimsy foams, you will recognise them by touch. Avoid. Brown felt was used 60 years ago.

Examples
www.wickes.co.uk/search?text=Lagging

Thanks PigletJohn.

We have a gas boiler and it’s that which heats the hot water and also the aga.

We have lived here for 20 years and the water cylinder was here when we came. We had a new boiler about 12 years ago (Worcester Bosch) and have controls similar the one a previous poster pictured, but can set different timings for hot water and heating.

I don’t think we have an immersion heater.
We had a pump added when we had an en-suite bathroom out in the Loft about 5 years ago. At the same time,e xtra loft insulation was added and the house is warmer now.

Our gas usage is 25,000 kwh per years. I know it’s because of the aga and it will need to go. Luckily we got a 2 year fix for energy in June 2021, so that lasts us until the end ofJune this year. We are keen to keep our gas bills as low as poss this year too, and saving the energy discount we get given by government for next year when our bills will be higher.

Is having the water thermostat on cylinder set to 60-65 about right?

We will look to lag the pipes which don’t have it. Some do and some don’t.

thanks again.

Legionella will die at 50C or above. At 50 it takes some hours, at 60 it takes minutes. At 70 it is instant. Hot water from a cylinder is more or less pasteurised, so in some places is safer to drink than from the cold tap, or an ice cube or washed salad or fruit.

In my house, the cylinder is well insulated and always above 50. The water is stored for hours on end so I'm not concerned. If I had a sports centre with multiple showers, or an old people's home, I'd be more careful. I don't want scalding water.

The cold water tank is more important, because water may be stored for long periods at about room temperature, or warmer in summer. Cold water tanks should have a clean, close fitting plastic lid, and be insulated. Not to protect them from freezing, but to prevent them getting warm. And to prevent pigeons or mice falling in and drowning

P.s.

Have a look for an immersion heater. You probably have one, and it will be useful on those infrequent occasions when the boiler is not working.

@WhatsitWiggle I have a similar cylinder and boiler and people to you. I have my hot water on for 30 minutes when we get home in the evening (for washing up after dinner and boy’s bath) and once at 9pm (for my shower the next morning and because I’m most likely to have the heating on at 9pm too). So 1 hour total each day. That’s ample for our needs and if I’m having an extra bath at the weekend or something I just stick the hot water on for an extra boost for half an hour before I start running the bath.

@B1pbop thank you - the thread has moved on a bit since I posted at the beginning of September! Unfortunately, my timer does not allow me to have different timings for the heating and hot water, but I'm reassured that I'm not heating water unnecessarily. There would be a slight saving each day if I changed the timer but not enough to justify the expense at the moment.

Whoops didn’t notice the September start, sorry! 😂