Shower pump/configuration for cold mains and low gravity feed hot

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Hi All

I moved into a ground-floor flat three years ago and the shower system has been causing me a lot of trouble. I am looking for a shower pump/configuration that could fix my problem.

I have attached a drawing of my system. I have a really low ceiling. In my system, the cold water is only cold mains. The water boiler is a vented hot cylinder. It is made out of some cardboard materials and it is mounted on the wall inside the airing cupboard. The cold mains feed the boiler. The hot water goes to the pump. The pump is only connected to the hot water. The pump is a "Watermill 2 bar Shower pump" and it has a negative head conversion kit installed to allow an extra air button to kickstart the pump. It looks to me the pump is connected in series. The mixer is connected to the cold mains directly. I really want to remove the air button. At the same time, I don't need to lower the showerhead to kickstart the pump. Does anyone know any better pump or pump configurations?

This is my pump: https://www.diy.com/departments/watermill-2-bar-shower-pump-h-190mm-w-220mm-l-340mm/38552_BQ.prd

The problem I am having are:
1. The air button and air hose break easily and they are very hard to be accessed in my bathroom. I broke 2 buttons already. Over time, the rubber of the air button and air hose become hard and brittle.

2. In order for the shower pump to start, I have to set the shower mixer thermostatic to the hottest setting. The water is very very hot initially, but I can adjust the thermostatic to a lower temperature after the pump is running for a few seconds.

3. When the showerhead is at a normal height, I have to use the air button to kickstart the pump. When the showerhead is placed to about knee height, it can kickstart automatically.

Thanks
PXL_20210904_122818960.jpg
 
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Replace the hot water cylinder with an unvented.

What you have currently got is a mess - generally you should pump both hot and cold to ensure equal pressure, however that's impossible with the type of cylinder you have.

Pumps can be obtained which work on negative head without the need for buttons, but that won't fix anything. The main problem is the type of hot water cylinder you have, that can't be fixed other than by replacing it.
 
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Thanks flameport.

I looked into an unvented hot water cylinder before. Have you seen one in a compact size? I am not sure if my air cupboard has enough room for it. I live in a studio flat.
Ok, Am I right that a negative head will remove the need for the air button but what is the equal pressure for? Is it only for the correct operation of the mixer? If so what problem will I encounter if I use an "adjustable pressure reducing valve" to match cold main pressure to the hot water pressure at the mixer?
 

CBW

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You could opt for:
  • an electric shower, fed by just the cold main, although most have feeble hot water delivery.
  • A power shower - these have a pump built in and utilise the gravity hot and cold supplies
  • An upgrade/conversion to a combination boiler
  • An unvented cylinder as suggested
 
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Thanks CBW

I couldn't find any power shower that allows the gravity hot and cold mains. Do you know any model recommended?
 
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I don't know if they're still made, but you used to be able to buy a venturi shower that utilised the pressure of the cold mains to entrain the gravity HW.

Haven't seen one for quite a while, worth looking though.
 
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Have you seen one in a compact size? I
Unvented cylinders are available in a wide range of sizes and shapes, including slimline and as small as 60 or 70 litres.
Very likely smaller than the thing that's there now.

Thermostatic mixers are designed to operate on supplies where the water pressure for both hot and cold is the same or very similar.
You can mess about with pressure reducing valves and other nonsense all day long - that might work, or perhaps not.

Ultimately the hot water system you have now is totally unsuitable for a mixer shower.
If it's one of those hardboard cased Fortic style things, it's very likely end of life anyway.
 
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