Confused need options - electric hot water solution

20 Jan 2017
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United Kingdom
Hot water for a bath, a wash basin and a kitchen sink.

Brought a 2 bed flat which has only electricity. It does have Economy 7 though.

It currently has a vented tank. The pressure is very low for the hot water taps. The cold water taps have very good pressure.

I want to take out the vented tank for one it is two big and takes up lot of space(looks to be about 140L capacity tank, we are just 2 ppl and don't need that much anyways), secondly, it does not have decent pressure.

I just need a system for the water only. The heaters are all storage heaters which are wire into Economy 7 circuit.

Could you people suggest me the alternatives that I need to be looking at with the main concern begin the hot water pressure. I am OK with storage as well as non storage solutions. Thanks!
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If you are using electricity then stick with stored 'off peak' water heating. First of all, 'off peak' costs a fraction of the standard 'day rate'. Also, to heat a decent amount of hot water instantaneously, suitable for filling a bath would need an electrical supply beyond what's available in domestic properties. So a stored supply that can be heated over time by a smaller heater is more viable.

So, you are back to the pressure. If you have a decent pressure & flow on your incoming main water supply, an unvented cylinder could be the way forward. They are pressurised by the cold main supply, rather than a header tank, so apart from some small pressure losses in the system you will get hot water at almost the same pressure as the cold main supply. However to fit them you need to be suitably qualified, they are quite expensive (£1,000 + installation) and need servicing every 12 months.

Alternatively you could fit a booster pump to the existing hot water cylinder, this would be the cheapest solution but the pumps aren't silent.
Your current cylinder is big enough for a good bath, plus several sinks. Or for a couple of reasonable showers plus washing up.

If you get a smaller one, it won't be, so you are liable to run out of cheap off-peak hot water and have to top up with expensive daytime electricity.

You mention pressure, but not flow. When you fill a bucket at the cold tap, and time it, how many litres per minute do you get?
Thanks for you reply. Yeah, pumps can be noisy, so maybe, need to rule them out. We normally use shower, so can live without having to fill a bath. Will that change the equation.

Thanks for you reply. The cold tap gets about 10L per minute. Is it a good flow? The hot tap the flow is bad as well. Just around 2 litres per minute.

Wondering if pump is the easy option, are there any in the market that do not produce noise, or am I wishing for too much :)
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We normally use shower, so can live without having to fill a bath. Will that change the equation.
You could fit an instantaneous electric shower which would have more pressure, flow is better these days with the newer showers rated at 10.5 kW (early ones were only 7 kW) but they still don't give as much flow as a pump or a unvented system.

are there any in the market that do not produce noise, or am I wishing for too much.
Some are quieter than others, but I've never come across a silent one. [Stuart Turner seem to be pretty good] If you do manage to find a quite one, let me know and I'll replace mine. Having said, that we don't really notice it now, once we got used to it.
2lpm is amazingly poor. Is that all you get from the bath hot tap? Or is it a modern fancy sink mixer that constricts the flow?

I suppose there is a small cold water tank on top of the hot cylinder. Is it raised up, quite close to the ceiling?

If you mostly have showers, an unvented cylinder will be your best bet.
The cold water taps have very good pressure.

Did you measure it with a pressure guage?

The cold tap gets about 10L per minute

I assume that's the mains?
You could have 10 bar pressure and 5/l min from the tap.
Either way its not suggesting a good set up for an unvented cylinder.

A monoblock tap on a basin supplied by gravity will give you a restrictive flow in comparison to a pair of taps on a more traditional basin.
A single traditional tap like these for example...

....will give you 14l/min @ 0.2 bar according to their specs. Maybe not possible in reality but double up with the second tap and you realise the advantage.
A good bath filler tap should operate down to a minimum of 0.1 bar.
If you have mains cold to one side and hot gravity the other it won't work very well imo.
Ceramic 1/4 turn taps are restrictive not to mention the small bore flexis.
Its all about how its designed and of course have the cistern sited as high as possible.

My first floor gravity system with 2m head delivers 7/L min on each basin tap.
The bath filler delivers 14/l min on hot and the same on cold run separately.
Both on together it fills the measuring cup @ about 22/L min.
These are old traditional gland and washer type taps.

My Docm monobloc mixer with ceramic disc and restrictive flexis on the ground floor only delivers a maximum of 6/L min on cold and slows to about 4/ L min swung unto hot with a 5m head.
Reduce that head to 2m and it would be useless.
I do keep the aerator checked for debris.
The showers in both cases under performs and would not be acceptable for most people.
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