Thermostatic Mixer shower can be fitted to Mains and Gravity Hot?

[acctofquestioniness]

Hi all, I've been researching and planning a job for my home the past few days and a few pieces of advice would be welcome to help me along the way.

I have a cloakroom toilet which has a toilet and a sink, where the sink currently is there is good room to put a small shower cubicle and a shower.

I was just wondering can a Thermostatic shower be fitted to the sinks existing pipework?
The cold pipe is a tee off of the Mains cold water pipe into the house and then the hot pipe is gravity fed from a hot storage tank in the floor above.
Are there any problems with this if someone turns a cold tap on or something happens with the Mains pressure?
Are there any problems with this if someone uses the other existing shower at the same time? (the existing shower has a shower pump for its hot and cold water)
Should I research getting another pump for this new shower with gravity fed pipes into it, or some other solution please?


The other advice is I will get the old toilet replaced in the same spot it is now. For the sink replacement and due to losing room in this cloakroom if I put a shower in, there's limited places for a new sink. I've been looking at toilets with sinks in the top of them as a solution.
If someone has got one of these toilet/sink combinations or fitted some anywhere what is your opinion on them please, are there any issues to be aware of or are they a good economical space saver design?


Thanks to any who can advise

 

[Ric2013]

You may fit certain types of thermostatic shower to mains cold, gravity hot systems, but it's not generally recommended.

As far as safety is concerned, the thermostatic nature of the showers should prevent all risk of scalding, but you may get the odd bit of cold water if people are using other outlets as you are showering, same as with an electric shower. Ideally, every shower would have a dedicated supply from the stored water to avoid this... ideal world scenario, anyway, and then you might not even strictly need a thermostatic mixer (although, being a new shower room, I think it's now the law). Some thermostatic showers react more quickly than others (e.g. Grohe) and come at a price. Obviously if you have extremely vulnerable or sensory-impaired people in the house, reliance on a thermostatic shower might not be enough and you would be wise to ask others who have more familiarity with the TMV2/3 regulations as applicable to NHS and care home premises for specialist advice.

The reason it isn't generally recommended to mix different pressures is that, for a start, the Water Regulations would, strictly speaking, then require you to fit single check valves to BOTH the inlets and this will severely restrict the flow of hot water (sometimes check valves will even fail to open at all under low pressure, particularly a few weeks after being installed, leaving you with cold showers).

The other issue is it depends HOW high your mains water pressure is and HOW low your gravity pressure is. Some mixer valves recommend a maximum pressure inbalance of 5:1, and some do not recommend, or even claim their products are fit for, anything other than 'balanced' pressures.

Arguably a way around the problem could be to limit the mains pressure significantly by using a pressure reducing valve to bring it down to as close to the gravity pressure as possible and then, voila! you have balanced pressures. I have seen it done, and it seemed to work. But as the pressure will then be low, make sure the shower you fit will give adequate flow for your needs at the very low pressures we are talking about (could be as low as 0.1 Bar working pressure at inlet).

If you're going to go for a pumped solution, you might consider getting a whole-house pump to pump the water to ALL your hot taps and showers, and, provided your shower mixers are both thermostatic, this could be a good way forward and would mean you could consider using one pump for the whole house.

As far as the other shower is concerned, IF it is installed correctly, a pumped shower will have dedicated pipework from both the cylinder and the cold water storage cistern, so should not affect, or be affected by, other showers in use in a meaningful way.

 

[SimonG]

Maybe look at an electric shower.

 

[Timmy D]

I’ve fitted one. I made an executive deduction and installed it without the customers knowledge during a bathroom refurb. She loves it. It does the job it’s designed for.

I quite like it.

 

[acctofquestioniness]

<Snipped>

Thankyou Ric for all of that information, I will go through it all over the next few days. I appreciate the time for the detailed response, thanks again

 

[acctofquestioniness]

Maybe look at an electric shower.

Thankyou, I will add it as a possible solution.

I’ve fitted one. I made an executive deduction and installed it without the customers knowledge during a bathroom refurb. She loves it. It does the job it’s designed for.

I quite like it.

View attachment 81234

Ok great thankyou. That room is a similar width to the one I am planning for and where my toilet is there is a window with a sill behind, so a sink like that will be ok for washing hands and a mirror can go on the sill for anyone wanting to shave or they can use the main bathroom. I appreciate the picture in a realworld environment, I think I will go with one of these toilets.