No hot water from shower - any suggestions

licklerose

Hi there,

I am hoping someone can offer some help/advice to a problem we came across yesterday:

One person had a shower, no problems, plenty of hot water. 5 mins later someone else used the shower, but there was no hot water coming through at all. We tried the other taps in the flat and all were coming through hot, just not the shower. Tried it again later and still no luck. We can get hot water through the tap in the bath (but this is at the opposite end of the bath to the shower), but not through the shower.

Any suggestions before I call a plumber to look at it?

Myser

What type of shower is it? Electric, mixer?

If it is a mixer, it could be that the hot water valve may need cleaning/replacing.

licklerose

Thanks for your reply - I guess it's a mixer. It's definately not electric, but it doesn't have a hot and cold tap, just one temperature control and one flow control.

Myser

Can you post the make and model or a picture?

macman

Sounds more like electric to me...

licklerose

It's definately not electric, I will try and post a pic later when I get home, but having just done a bit of googling, it is a thermostatic mixer. Not sure of the make at the mo

candypop

I had same problem with my mira mixer shower which runs from my combi boiler sometimes the water would be hot and other times cold. The diverter valve in the boiler had broke. Cost £70 to have replaced. May not be your problem but worth checking out.

2sides2everystory

You live in a flat - what floor?

Can you hear any electric pump starting when you run water either into the bath or diverted into the shower? I would guess not.

My guess is that you are suffering from those oh so kind water companies having willy nilly reduced pressure all over the country in order to save themselves the cost of fixing leaks in the network.

My personal estimate is that it will soon have cost an average of £500 over the last 5 years for every household countrywide just in plumbing bills to work around it, let alone the wasted money in replacing showers that were thought to have "worn out".

Like all big corporates, the water companies just don't care.

Keeps plumbers busy of course.

Now then, it is possible that your set up is a little like mine.

If you live in a flat with a cheap unpressurized plumbing system (like mine), there is a good chance that your hot water tank is gravity fed via a small mains cold water header tank in the top of the airing cupboard. The header tank really has just two purposes
(1) to separate the cold mains network physically from your hot water system (so no backflows are possible which might mix your dubiously heated and stored hot water with the cold mains in the street) and, more importantly for your shower,
(2) to create a head (i.e. a pressure) for the hot water given that the mains pressure is not available to it since the header tank arrangement has separated the two as described in (1).

Your header tank may appear very small. The laws of physics allow that it could be jamjar size and still work so long as it fills as fast as you use hot water and the jamjar is held high enough.


If you have such a system then as soon as the header tank is empty (and it will become so after some minutes of running the shower if the hot water is being used faster than cold water is refilling the header tank) then quite simply the hot water will "lose its head" (lose its pressure). At that point there will no longer be sufficient pressure for it to get through the mixer and back up to the height of the shower head (which if you think about it cannot be higher than the water in your jamjar). Jamjar empties and water level drops through the bottom and in fact drops way down to waste height around the top of the hot water cylinder means that you'll only now get hot water out of he shower head if you hold it down around waist height or indeed the level of the bathtaps perhaps ... you can still get hot water from the bathtaps right?

So, if jamjar / header tank empties, very soon all that then remains flowing through the mixer is the mains fed cold water which arrives directly at the mixer via a different route, and which is still high enough to get through to the shower head, even though it is not at sufficient pressure to keep the header filled for the hot water cylinder.


Now, this post might actually have nailed it in one, but there are many variations, and sadly, if your hot water system is a pressurized one, then you really shouldn't mess about without qualified help as I understand it can be dangerous (never had one myself).


PS If I have nailed the problem (and you may be able to check it by running the shower till the header tank is visibly empty and then seeing if the shower has gone cold then what can you do about it?

Mine runs for about 6 minutes which is sometimes not enough for women rinsing their hair! So I have been known to top up the header tank with a bucket from the kitchen sink during their shower to keep the peace! It works perfectly well if you have enough room in your cupboard to get to the top of the header tank.

Else the obvious solution is a bigger header tank.

The suggestion that you waited for a period and it still didn't work is a bit worrying and is perhaps the one thing that blows a hole in my argument. In my case if I shower for 6 minutes then I wait 3 mins for the header to refill then I can get another full 6 minutes of hot through (actually it depends on time of day and demand in the street - the street pressure varies quite a bit at peak times).

There may be some real plumbers along - and Myser might well be onto something with much shorter posts than mine - will be interesting to hear what they have to say if you can give a bit more info about your system.

Good luck.