Filling up a hot water tank more frequently

[Joleigh]

Hi,

I am a total layman when it comes to this subject so please bear with me. I have a hot water tank that works off an immersion heater (Economy 7). The problem is if I use a relatively small amount of hot water in the morning (e.g. to do the washing up) I won't have enough hot water to fill a bath in the evening (also I have to press the boost button before my bath but I presume this is normal). This is a problem insofar as I would like to do washing up every day but I also like to have baths frequently (especially as my electric shower is abysmal - another subject entirely). I have found to my horror that I have started to let the washing up slip just so that I can have a hot bath. Not a good habit.

The hot water tank refills and heats up overnight (Economy 7), I would like to know if there is a way to get the hot water tank to refill during the day also. From what I can gather it's the lack of water in the hot water tank in the evening that seems to be the issue. If I press the boost button beforehand, whatever is in the tank seems to heat up fine. If it costs electricity to refill it during the day, I don't mind.

Any thoughts appreciated,

Thanks

 

[copea]

I wouldn't expect the relatively small amount of hot water used when washing up to deplete the supply to the extent that you can't have a bath in the evening unless there's another issue.

How big is the cylinder?
Is the cylinder and the pipework leading to/from the cylinder insulated?
Do you have two immersion heaters (one at the top and one at the bottom) or just one?
If you don't use the boost facility, do you get any hot water at all?
How much do you fill the bath? Is it a regular bath, or a particularly large bath, like a corner bath?

 

[Joleigh]

Thanks for the quick reply.

The cylinder is insulated so I can't see any labels but with the insulation it's approximately 90cm high x 40cm across if that helps.
I'm not sure about the pipework, from the pipework I can see in the airing cupboard, it's not insulated but the cylinder is. The rest of the pipework may be though.
If I don't use the boost facility, I think the water in the kitchen sink and basin is still hot for a while but if I try to run a bath it will be luke warm and half full before it turns freezing cold (this is usually in the evening). I guess it probably starts out hot briefly.
It's a regular bath, and I would normally fill up to the overflow or just below, essentially so the water is covering me.

 

[oldbuffer]

1. Assuming 50mm insulation at top, height of cylinder is 850mm.
2. Assuming insulation of 50mm either side, width is 300mm (sounds very small)
3. Capacity is (0.85 x (.3 ^2) x "Pi") = (approximately) 240 litres. Usable hot capacity probably 3/4 of this, say 180 litres
4. Average bath is 80 litres, but if you are filling almost to the overflow, say 100 litres. Of this, probably around 60 litres will be hot water.
5. On the basis above you should be able to get a bath as well as doing the washing up out of one overnight "re-heat", and probably a second bath.
6. I'd be looking at whether or not the lower immersion heater (the economy 7 one) is working, as it sound to me as if only the top 1/3rd of the cylinder is heating.

 

[Joleigh]

That's interesting thank you, I will check the lower immersion heater if I can. Incidentally, I don't even use the cold tap while filling a bath, as the hot water will run out and turn cold about half way through filling if not sooner (if I've done washing up).

 

[JohnD]

From what I can gather it's the lack of water

no, the cylinder is always full of water. But some of it is cold.

If you have an upper and a lower immersion heater, the only way to have (almost) the whole cylinder hot, is to turn on the lower one. The hot water rises, so each heater will only warm water at and above its own height.

Horstmann (and probably others) do immersion timeswitches that enable you to override the timer.

please show photos of all the switches, timers and cables around your immersion heaters; and of your consumer unit(s) and electricity meter(s). There is probably a timer close to your meter, owned by the electricity company.

If you own the house, and have no gas supply, consider having a larger hot water cylinder fitted.

from your dimensions, I think your cylinder is 36" x 14" or thereabouts, so the capacity will be (only) about 100 litres, not 240. I didn't calculate that, it's what they are.

What colour is the insulation? New ones have more.

 

[Joleigh]

I can't see anything that looks like a lower immersion heater, but the insulation could be in the way? I did just have a feel of the tank underneath and it did it feel warm at the bottom if that means anything.

I do own the house, moved in about 6 months ago, and there is no gas supply to the village. If a larger hot water tank is required then I will be happy to get one, but it will have to go in the loft as there is no room in the small airing cupboard where the current one is situated. I'm guessing that's OK? I would need access to the controls/switches though, ideally without having to go in the loft each time.

The insulation is red, I have attached some photos as requested. You can ignore the warning sticker on the consumer unit, that was placed there while the property was vacant by the repossession company who were selling the house. They don't come off easily!

 

[JohnD]

The insulation is red

Ah, it looks like you have a bare copper cylinder, with a red fibreglass jacket on it.

More modern cylinders have factory-applied stiff plastic foam insulation. I should think yours is 30 years old or more.

Being small, and the insulation not the best, you will always tend to be short of hot water. You could add some foam pipe lagging, especially on the pipe that comes out of the top. You can add a second jacket on top of the first.
https://www.wickes.co.uk/search?q=laggingrice-desc


From what you say, there is probably just one immersion heater, going in at an angle from the domed top if the cylinder. They are usually about 30" long so it will not quite reach the bottom. If/when you get a new cylinder, it can have two heaters going in horizontally through the side, the bottom one will heat the whole cylinder, and the top one will heat about a quarter of it. as you have cheap-rate night electricity, it is best to use the bottom one at night and to top up as little as possible during the day.

The immersion heater will take round about an hour and a half to heat 90 litres of water. It looks to me like you can put on your "boost" prior to having your evening bath, the thermostat will turn it off as soon as the cylinder is hot, so you will not waste electricity. Your Horstmann immersion timer switch is a good model, but check your electricity tariff to see what hours your cheap rate is, and set the timer to take full advantage.

Old immersions often have bad thermostats, which can be very dangerous if they overheat. Please use a thermometer to test the temperature of your tap water when it is fully hot. About 60C is OK. In summer a bath at about 50C is hot enough. Legionella does not multiply above 45C, and is killed fairly quickly at 60C. you are more likely to have bugs in your cold water loft tank, which in summer, uness well insulated, may be rather warm and at an ideal temperature for bacteria to thrive.

If you have a really good flow of cold water into your house from the watermain, you could have an unvented cylinder when the time comes to change, it can give excellent hot water delivery. You may need to upgrade some of your pipes and stopcocks.

It looks like you have a 3-phase supply. Are you in agricultural or industrial premises? Or at the end of a long overhead power line?

p.s.
If you have a fireplace with a back-boiler (often found in rural districts) or if you are thinking of buying a multifuel stove, you can get one that will heat a HW cylinder, which is very convenient in winter, to save electricity. It take a small fraction of the heat of the fire, so you won't notice it, but the water will always be hot while you have a fire in. It does need professional installation, for safety.

p.p.s.
The immersion heater costs about 45p an hour during the day, and about half that off-peak, and heats water at the rate of about 1 litre per minute, so enough to fill a bath takes about 90 minutes. If the thermostat and insulation are good, it will turn itself off once the cylinder is fully hot. Your insulation is substandard, so it might waste somewhere around 30p a day in lost heat. A modern cylinder, maybe a quarter of that.

 

[AdvanceHelpline]

You need a bigger cylinder to take advantage of off peak power , and a modern one - perhaps think about unvented (mains pressure) for a decent shower, too. If you live alone I would suggest a 210 litre.

 

[Joleigh]

Thank you so much for the responses, I have learnt a lot. I now understand what I am dealing with and what I need to do to fix the issue and it seems if I get an unvented it will solve the shower problem also (the pressure can't be any worse than what I get now). Time to get quotes! I am actually planning to get a new wood burning stove this year also for heating as the electric heating I have at the moment is inadequate and very expensive so I'll explore the option of heating the HW cylinder with it.

I'm not on agricultural or industrial premises and I don't think I am at the end of a long overhead power line, I'm pretty central in the village. I hadn't even noticed that I had 3 phase supply so that's interesting.

 

[copea]

Do you know if you definitely have Economy 7?
It's more unusual with three phase supplies, although it does exist.

 

[Joleigh]

Yes definitely, the first thing I did when I moved in was get the cheapest economy 7 tariff I could as I knew coming from a gas supplied home, electric heating was going to be a lot more expensive.

 

[copea]

Good, good.
An unvented cylinder will potentially address the low water pressure issues, but you'll need to check your incoming mains pressure and flow rate first, as it could end up being an expensive mistake if you haven't got sufficient 'oomph' in the mains to drive it.

The bonus will be that the cylinder's insulation will be up to modern standards, and with some insulation on the pipes within a metre or two of the cylinder, the standing heat losses will be very low.

As you like baths (even though this is possibly because of the dodgy shower) they'll also run a lot quicker as the hot and cold supplies will be at mains pressure.

 

[JohnD]

You can get a multifuel stove that will run enough radiators for a house, but it's pretty big. One that will do a cylinder, and, say, the bathroom radiator, will be more normal.

Get multifuel not woodburner. Wood burns faster and contains less heat than solid fuel. Even if you have plenty of wood, keep a few sacks of solid in case, say, you should run out or be ill and unable to saw it up or bring it in.

 

[JohnD]

You can get an idea of incoming water flow by filling a bucket at the kitchen cold tap, timing it, and calculating litres per minute. Repeat the test at garden tap and scullery cold tap if you have them. When you get quotes the plumber should test pressure as well. Sometimes it's necessary to lay a new, larger pipe out to the watermain under the pavement. This is not difficult or complicated unless it is a long way or there is a concrete drive. It does not have to follow the same route as the old one, and plastic pipe is flexible on a long roll so doesn't need bends and joints.

If your old pipe is lead, ask your water co to test your drinking water for lead content BEFORE starting work as there may be a subsidy or other assistance. They can be very slow to make appointments so ask now.