# Problems fitting shower -combi boiler - lack of pressure

I've got a tricky situation here - a combination boiler one side of
the corridor, and the bathroom directly on the other side. The pipes
go down, under floorboards, and up again to bathrom taps.
I've tried fitting that cheap rubbery shower with two rubber thingies
that fit onto the tap-head, but as soon as you raise the shower head
by more than a foot above the taps, the water stops running. Theres
simply not enought pressure.
I've been told that I need a waterpump or shower pump - but I heard
this doesnt work with combi boilers. I know you can buy electric
showers that heat up the water, but this will need to sit about a
metre above the taps, and there's not enough pressure.
Does anyone have any cheap solutions at all?
Thanks
J
Something does not add up there...
what is the mains pressure like at the cold tap in the kitchen? Can you arrest the flow by sticking you hand over the end for example?
Where is the combi in the house (upstairs or downstairs)?
What make and model is it?
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D\
=A0 =A0 =A0 =A0|
=A0 =A0 =A0 =A0|
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D/- Hide quoted text -
Hmm, yes, actually, taking a second look, it doesnt add up! I've missed some sitters! Perhaps I'm wrong. I should add, that its my girlfriends flat, and I've just moved in, and she wants a shower, but cant get one. She told me she had a combo - hot water and gas central heating. I assumed she ws right. Anyway, it looks to me like the layout in the bolier comparmtnet is like this: there's an immersion boiler top left, (electric Im assuming) Underneath, bottom left, theres a gas boiler. I dont know if this is a combi. Top right, adjacent to immersion, theres a water tank. below this is the timer set up. below that, on floor, theres seems to be what looks like a pump! The immersion boiler is Heatrae-Pullin, with a honeywell thermostat (connected to Honetwell timer controls) Gas boiler is a Potterton Profile.
To answer your question, you need a very strong thumb to stop the cold water in kitchen. Its much easier to stop the water in the bathroom with thumb. Bear in mind, however, that the kitchen is directly behind the boiler compartment. Also, this is a flat on an estate, built in thirties, and the flat is on the fourth floor.
It might be easier if I take a picture. Are we allowed to post pictures in these groups? Cheers
The Profile is a conventional heating only boiler, not a combi.
Yes a picture would be great. You can't post it directly to the group but you can put it on any of the free picture hosting sites and post a link to it here.
So, reading between the lines a bit, it sounds like you have a traditional gravity fed system with a header tank. This explains the lack of pressure in the bathroom since the cold tank is presumably in the flat and not in the attic space above it. It may be that a pump was fitted to overcome this limitation in the past, but that may no longer be working.
Hot water is provided possibly by an electric immersion heater, or maybe in addition the gas boiler (won't know for sure without seeing the type of cylinder, and arrangement of pipes etc.
On Sat, 19 Jan 2008 09:18:46 -0800 (PST), snipped-for-privacy@hotmail.co.uk wrote:
No pics here but use a third party host like Photobucket.com and post the direct link here .
OK, here are the pics ...
are sideways, unfortunately.
Looks like inside of spaceshuttle.
Cheers chaps, all help appreciated.
The red cylinder near the floor in photo 2 etc,. is a pressure vessel for the central heating circuit.
The braided hose from the grey valve in photo 5 is the means to fill the Central Heating and pressurise it.
The red object on the right in photo 6 angled down slightly is the pump for the CH circuit. The gauge behind it is a pressure gauge for the CH circuit. There is probably a pressure relief valve for this circuit
You have a HW cylinder above the boiler in photo 10. The two pipes are to connect the boiler circuit to it with the small brass device being an air vent. The larger one below is a 3way valve used to divert heat from going to the CH to the HW cylinder instead.
In photo 12 there is the drain cock at the very bottom, then immersion heater and cylinder thermostat above that.
This is not a combi as far as one can tell.
The real question is whether the cylinder is open vented or pressurised.
If you take the head off of the shower and put your thumb over the hose, set the control to hot and turn on the shower, is there enough pressure to force your thumb off or feel like it will? What about the cold?
If both feel fairly weak in comparison to the mains cold in the kitchen, then you need a dual pump.
A good quality choice is the Stuart Turner Monsoon or Showermate. e.g.
are a little more expensive than the cheap ones in DIY supermarkets, but are substantially better quality and will last a lot longer. This is a purchase where you do get what you pay for.
OK, had to load some of those into photoshop to work out what was going on....
Anyway, it makes it pretty clear what you have.
Andy has highlighted the major components on what is a fairly conventional heating and water system using a conventional boiler (not a combi). The boiler has been configured to run a sealed system on the primary side - and this dispenses with the small CH header tank that you may find on other installations. The three port valve is used to direct the flow of hot water from the boiler either through the radiators or through the heating coil in the hot water tank (or possibly both at once if required and if it is a mid position valve).
The only pump you have in the system is the main circulation pump (red thing at a jaunty angle tucked under the cold water tank). This has nothing to do with the flow of water from the hot taps.
So back to the shower question. The main limitation is, as you have discovered, lack of head. The shower will not run should the shower head be raised above the height of water level in the black cold water tank. Since this is a flat and this is on the same floor level as the shower - that probably means 4 to 5 foot off the floor level.
The simplest solution would probably be to add a shower pump. In this case it may possibly need to be a "negative head" shower pump. (another option may be a venturi shower, if you can get a cold mains supply to the shower.
OK all, some good links there, and great analysis. You've both obviously spent a substantial time going over the layout, and I thank you both for your help. I have to say, I dont really understand 'entirely' what you're both saying, and I'd love to fully understand how the whole thing works, but I feel a bit embarrassed to ask for what would effectively be free training. I think I'll consider that shower pump, leave it on the floor near the downward pipes, and use flexible hosing to follow the other pipes into the bathroom. Quite alot of work actually! perhaps better leave to experts.
OK, massive thanks to you both. J
Have a look at Ed's sealed system FAQ since this will nicely explain how your system in particular works:
are some other pages we prepared earlier:
?title=Category:Heating
Depends on where you put it and how you plumb it.
On Sun, 20 Jan 2008 05:38:55 -0800 (PST) someone who may be this:-
You could always do a little research for yourself, for example taking a book out of the library and then asking about anything that isn't clear.
Flexible hosing is flexible, which may lead to it vibrating more than anticipated. Most standard types of pipe one will see in buildings are also flexible, but rather less so.
I reckon the tank and cylinder may be a Harcopak [1] (there seem to be a enough angle iron around for one). The cupboard (as always) looks like it was built /after/ the Harcopak was positioned.
A boost pump (negative head) is the simplest way forward, if the pump can do just the shower/bath then that will save people being upset by the noise of the pump filling the WC cistern.
My guess is that the heating system here is 15-35 years old. The boiler may have been replaced a recently as mid 90s. Replacement with a combi is not called for - although it would be in the frame in (10 years?) time when the boiler is up for replacement.
[1] Which some people might well describe as a "combo".

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