Heating shower water - boiler (central heating) vs immersion problem

spalpeen · 28-09-2025 11:50PM #1

Hi,

Moved into a new place. If I heat the water using the immersion, even if I heat it for ages, the water goes cold within 6-7 minutes in the shower. However, if I heat it using the boiler, it stays hot much longer. But I don't want to always turn on the heating.

If I really have to put the heating on for a shower then I can live with it. But is it possible my water cylinder is defunct or needing replacement? In which case I can get a new one which will allow me to have a shower simply by putting the immersion on a timer? The other advantage here is that my heating does not have a timer, although I'm sure that can be installed (who does this??).

Basically I want to know if my cylinder is the problem or if it doesn't matter anyway because heating water via boiler is the best way to go, as it seems to also be cheaper? Thanks for any questions or comments.

manatoo · 29-09-2025 12:18AM

Your immersion is only heating the upper part of the cylinder. That's either because the cylinder switch is set to "sink" instead of "bath" or it's because the immersion is only a single element, usually 9 inch immersion plugged into the top of the cylinder with no switch. If it's the former, switching it to "bath" will heat much more of the cylinder. If it's the latter, it will only ever heat the amount of hot water you're getting and the only way to heat the whole cylinder is as you said, to use the central heating system

Wearb · 29-09-2025 12:28AM

If you can heat the cylinder separately (not heating rads at same time) then you are most likely working out cheaper using your boiler.

In the colder months, there's nothing wrong with heating rads and cylinder together.

greasepalm · 29-09-2025 01:23AM

Yes agree element is too short or tank is short and not allowing capacity to heat. My element is cooked as not working and if weather is bright my solar panels will give some hot water. As colder weather is now here using Gas to warm the house also heats up water in the cylinder to have a nice hot shave Nice.

spalpeen · 29-09-2025 09:46AM

https://www.boards.ie/discussion/comment/123860196#Comment_123860196

It's set to bath. If I get a new cylinder, and if its bigger, and i use the central heating to heat it, will this mean i will have more hot water for longer? I presume getting a new cylinder wont improve the immersion being only at the top of the cylinder, unless the new cylinder comes with a dual element?

I just checked the cap of the cylinder and it says dual element and it says boost

spalpeen · 29-09-2025 09:47AM

This is what I have been doing but now as October approaches I want to use the heating. It is a bit annoying though with immersion as showers have to be maximum 5 mins.

https://www.boards.ie/discussion/comment/123860204#Comment_123860204

manatoo · 30-09-2025 10:34PM

https://www.boards.ie/discussion/comment/123860497#Comment_123860497

Can you post a picture of the label on the top of the immersion cover? I'll take a look at the specs of the immersion if you can.

Just so you know, cylinders don't come with immersions. If you buy a new bigger cylinder and you want to heat all of it with an immersion then you need to buy a bigger immersion with a longer element on it. They come in a wide range of lengths.

John.G · 01-10-2025 10:26AM

If a new cylinder is being considered its better to try and get one with side mounted immersion elements but only if the bottom immersion element is installed below the heating coil, otherwise the top mounted dual element is better, I have seen them available, the whole cylinder contents can then be electrically heated, if required, and the coil more or less likewise.

spalpeen · 10-10-2025 10:52AM

https://www.boards.ie/discussion/comment/123865896#Comment_123865896

Hi, apologies for delay and thanks

John.G · 10-10-2025 03:55PM

Have got a "smart" electrical meter??. this has a pulsing on/off red LED, 1000 pulses = 1.0kWh

If so when the HW cylinder is lukewarm, ensure the immersion is selected to sink and switch it on, then ensure heavy users like dish washer, washing machine,electric kettle, toaster, microwave etc or whatever are off, then get a "stopwatch" and start it immediately after the first pulse, keep watching the LED closely, after 15 pulses, stop the timer and note/write down the reading in seconds + any decimal places. Then select BATH and again measure the time taken to do 15 pulses. I would expect the 2.0kW sink element to take 27secs to do 15 pulses and the 2.8kW Bath element, 19.5secs to do 15 pulses.

Heating shower water - boiler (central heating) vs immersion problem

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