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By Ches Cherriman
#8073
Before the lockdown I bought a bathroom suite. This is to replace an adequate electric shower.

I had good hot water flow but explained to the salesman that I have a complicated system. The boiler is a combi but it feeds a hot water tank on the ground floor. There is also a water tank in the loft which I now believe is what feeds the system. There is a ground floor shower which is quite adequate. The salesman recommended a thermostatic bath and shower mixer. This is an aqualisa Midas 100.

When I fitted the mixer there was no flow to the shower. On cold only (i.e. blank off hot water), the shower diverter valve just stayed 'up' i.e. not a lot of pressure.

I tried to contact the bathroom shop but it is in lockdown, so I contacted aqualisa. They recommended I check the water pressure.

I bought an inexpensive water meter which indicated that the hot water pressure was low and the cold was 1.5 bar (the minimum the mixer will work at is 1 bar).

So now I am trying to find out what I should do ...

Should I

- Revert to an electric shower

- Add a pump to the hot water feed to bring the pressure up to 1.5 bar (and would this be enough to guarantee a good shower)

- Add a pump to both hot and cold feeds to bring the pressure up to, e.g., 2 bar

The technician from aqualisa didn't seem to know too much about whether this would work or not
User avatar
By Croppie
#8076
So, if I get this right, your combi boiler feeds the ground floor shower and probably the kitchen.

Your timeclock should have a DHW setting for the primaries for the cylinder which would have the secondary side fed from the tank up in the loft. This tank, I believe, solely feeds the cylinder.

You have mains water coming in on the cold water side. This is giving you unbalanced hot and cold water supplies which the thermostatic valves can't cope with,

I would, assuming you have a halfway decent flow rate which you suggest is fine going by the other shower, do away with the tank in the roof space and replace the DHW cylinder with an unvented tank and ensure that the cold feed for the shower and bath is taken off after the combination valve to keep both hot and cold balanced.

This isn't a DIY job as you need a G3 ticket to fit an unvented cylinder.

Your other ideas, except for the electric shower, aren't really feasible and could in fact be dangerous.
By Ches Cherriman
#8097
SimonG wrote:
May 19th, 2020, 3:28 pm
Wouldn't have thought it was a combi boiler, maybe a condensing boiler.

If cold and hot are tank fed then go for a pump. Stuart Turner pump. Then you need to see if you need a positive or negative head pump 👍

thanks SimonG :) , the boiler is a Worcester Bosch Greenstar Ri if that means anything ! Hot is gravity from a few feet above but I assume positive head pump. Cold is mains at 1.5 bar pressure
By Ches Cherriman
#8098
Croppie wrote:
May 19th, 2020, 3:47 pm
So, if I get this right, your combi boiler feeds the ground floor shower and probably the kitchen.

Your timeclock should have a DHW setting for the primaries for the cylinder which would have the secondary side fed from the tank up in the loft. This tank, I believe, solely feeds the cylinder.

You have mains water coming in on the cold water side. This is giving you unbalanced hot and cold water supplies which the thermostatic valves can't cope with,

I would, assuming you have a halfway decent flow rate which you suggest is fine going by the other shower, do away with the tank in the roof space and replace the DHW cylinder with an unvented tank and ensure that the cold feed for the shower and bath is taken off after the combination valve to keep both hot and cold balanced.

This isn't a DIY job as you need a G3 ticket to fit an unvented cylinder.

Your other ideas, except for the electric shower, aren't really feasible and could in fact be dangerous.

thanks Croppie, Sorry it took a while to get back, I didn't really understand this ! Anyway, the mains pressure is 1.5 bar and I wondered if this would be sufficient to drive the aqualisa thermostatic mixer and give a decent shower. The other shower is downstairs - I assume it is gravity fed, but it gives a decent flow
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