How to get a thermostatic shower from a gravity copper tank?

ThisIsWeird

bobfredbob said:

Can someone explain the options?  I was brought up on a simple electric shower.

My house has a system boiler with an old copper hot water tank (approx 120 litres), and cold water storage tank is probably around 220 litres.  The upstairs bathroom has no shower at all.  The downstairs shower was an 8kw electric shower, but that is on its way out.  We'd like to refit upstairs to a be a shower only and get a downstairs thermostatic shower.  We'd probably only use one shower at a time.

Downstairs, we've been using the non-thermostatic bath mixer tap for the shower.  But we have problems getting a stable temperature and we have young children and soon to have an elderly relative staying.  It reaches a stable temperature for several minutes, but then it will suddenly get scalding hot even with no other hot water drawn.  Perhaps water mixing in the tank after a couple of minutes means hotter water is flowing?

So, I thought a thermostatic mixer.  But I have trouble finding a good low pressure thermostatic bath mixer taps.  Most have very poor reviews or refuse to give the litres per minute.  I saw some shower-only mixer bars that deliver 3lpm, which is even worse than my electric shower.

Do all low pressure thermostatic mixers have poor flow rates due to their mixing?

For a little more, there are a number of power showers.  But, I think I'd need dedicated pipework from the water tank to both of the bathrooms?  So the plumber couldn't just hook in to the existing bath plumbing?

I had two people in to quote for an unvented cylinder.  Both said it was difficult to do the discharge piping.  Neither supplied a quote.  We get around 25lpm I think.

If we had the cylinder replaced with an unvented cylinder under the stairs (where it might be easy to run pipework under the floorboards), would we hear it filling up or other noises?

However, we're not sure we like the idea of having to get it regularly serviced.

In the past, I'd be tempted to just fit a combi and get high pressure everywhere.  But, with the government all confused over gas and on-demand combi-boilers/electric showers and wanting to "encourage" a reduction in gas, it seems we should perhaps stick with a tank instead of fitting an electric shower upstairs and downstairs.  But, I'm open to ideas and any experiences.

Most of the options have been nicely covered.

Taking a step back, you say you have a ~25lpm mains supply? Any idea of the pressure behind this? Does your cold kitchen tap gush strongly, for example? Did any plumber measure this as part of their 'unvented' quotes? I assume they must, at least, have considered your mains supply 'adequate' for an unvented?

To answer your Q, no, you won't hear this type of cylinder 'filling up', because it doesn't. It is always full, and under mains pressure - as hot is drawn off, the cold mains replenishes it. 

So, if you reckon you have an alternative location for an 'unvented' that will work, and the cost won't be excessive, and your 25lpm is being delivered by at least 2bar (hopefully more), then I'd suggest it's the system to go for. All 'passive' - no nasty pumps, and you'll even lose that nasty CWS in t'loft.

Plenty flow all 'round.

ThisIsWeird

There used to be a Triton 'power' shower that looked just like an electric type, but had a wee, low voltage, pump inside it. It would whirrrr into life when turned on, and deliver a really nice shower from a weak vented system. Not sure you can still get them, but what a mistake if not. Cracking wee beasties.

BUFF

you mean https://www.tritonshowers.co.uk/powershowers ?
Thermostatic too.

Mira  (& no doubt others) also do them https://www.mirashowers.co.uk/showers/power-showers/

ThisIsWeird

BUFF said:

you mean https://www.tritonshowers.co.uk/powershowers ?
Thermostatic too.

Mira  (& no doubt others) also do them https://www.mirashowers.co.uk/showers/power-showers/

Thanks! :-)

Triton 14lpm (roughly twice as good as an instant leccy shower), and the Mira 16lpm - the latter should certainly be ok. But, what a price! And you'll need two.

Unvented looking promising :-;

bobfredbob

Sadly, neither unvented guy measured the pressure (or sent an actual quote).

A few years ago I measured the pressure at the garden front tap (next to where the water supply enters the house) with the tap on full and it was just over 2 bar.  The house taps are all 25+ years old, non-aerated and quite slow; a boiler guy a few years ago said they were limescaled.

We still have lead water mains, so things should get better if it were replaced (but costly).

The one reason I was thinking of relocating the tank under the stairs is that it would then be near the water mains so have the best possible pipe run.

I think I will try and find another G3 guy first, since they can always quote for a pump if they can't do it.

grumbler

bobfredbob said:

A few years ago I measured the pressure at the garden front tap (next to where the water supply enters the house) with the tap on full and it was just over 2 bar. 

If you measure pressure at the exit of the tap, it doesn't depend on whether it's opened fully or partly.  Only the flow depends on this.

Generally, static pressure can be high but can drop significantly at higher flow. At the maximum flow it's close to zero. This is normal if this flow is high enough.

I was thinking of relocating the tank under the stairs is that it would then be near the water mains so have the best possible pipe run

Do you mean unvented cylinder?

ThisIsWeird

bobfredbob said:

Sadly, neither unvented guy measured the pressure (or sent an actual quote).

A few years ago I measured the pressure at the garden front tap (next to where the water supply enters the house) with the tap on full and it was just over 2 bar.  The house taps are all 25+ years old, non-aerated and quite slow; a boiler guy a few years ago said they were limescaled.

We still have lead water mains, so things should get better if it were replaced (but costly).

The one reason I was thinking of relocating the tank under the stairs is that it would then be near the water mains so have the best possible pipe run.

I think I will try and find another G3 guy first, since they can always quote for a pump if they can't do it.

I think that's worth doing.

BUFF

ThisIsWeird said:

BUFF said:

you mean https://www.tritonshowers.co.uk/powershowers ?
Thermostatic too.

Mira  (& no doubt others) also do them https://www.mirashowers.co.uk/showers/power-showers/

Thanks! :-)

Triton 14lpm (roughly twice as good as an instant leccy shower), and the Mira 16lpm - the latter should certainly be ok. But, what a price!

Depends which Mira you get. In the real world (rather than MRP) you can get either Mira thermostatic or Triton models from ~£200.

ThisIsWeird

Cheers, BUFF. And phew.

There's a number of models, say at SF and TS, starting at ~£200 - the Mira 'Vigour' - and others - eg the 'Event' - for a bit more. Thermostatic versions of both.

I guess the latter is quieter?

BFB, I'd suggest that this could be a completely satisfactory solution, and possibly/probably the cheapest and easiest too.