Installing shower bath - totally baffled!

[MrMoo123]

Hi All,

Just installed a new shower bath and we decided to go for a bath mixer tap that has a shower connected.

All went well with installing it, but the mixer does not mix the water - the only way I can get hot water out of it is to switch the cold off completley and have the hot on full - which gives me scalding hot water and not at a great pressure. As soon as I turn the cold tap - it completley takes over and i'm left with icy cold water - even though the hot tap is fully open.

From what I can gather, the cold is clearly at a higher pressure so its totally taking over from the hot - and pusing the hot back down the pipe! As when I switch the cold off again, it can take 30 seconds or so for the hot to pick up temperature again.

What baffles me however is that I have a mixer shower coming off the same pipework in the en suite - and thats always got lovely warm water at a great temperature and all I have to do is move the mixer valve slightly into the hot to achieve this.

So what's going on and what are my options?

I thought it was the tap so I took that back and got a different one, which was suitable for low pressure systems. It barely made any difference, if any.

Is it because the mixer shower I have in the en suite has a thermostatic control so it controls the flow ?
So if I installed a seperate mixer shower in the wall over the bath it would solve the problem?

Or will I be wasting my money and should instead go for a shower pump? If so, how does this work with my existing pipe work? Can I just install it in the airing cupboard to boost the pressure of the hot water or do they not work like that? The pressure of the cold is fantastic!

Sorry to ask so many questions just I can't get my head around what the problem is and the best way to solve it. I'm clutching at straws and every person I ask or website I visit seems to say something different. Plus the Mrs is on my back as she wants me to start tiling and I don't want to that till i'm sure the plumbing is all sorted in case I have to hide pipes in walls!

 

[cider]

showers need to have ballanced supplies unless they are designed to work utherwise. if you want to have a shower off a bath mixer then ultimately you will run a new cold feed pipe from the loft tank to the bath which is probably how your other shower is plumbed

 

[MrMoo123]

I don't have a loft tank.

I have a large showermax tank in the airing cupboard. The cold sits above the hot.

I'm certain that the cold for the en suite shower comes from the same pipework as that feeds the bathroom - in fact i'm certain.

 

[cider]

dont know the name but your tank may have 1 high pressure outlet to run a shower (your ensuite) and the rest of the hot water runs off the storage at low pressure hence the pressure difference

 

[MrMoo123]

there isn't - there must be something in the mixer of the shower in the en suite that prevents this from happening. I know for sure because the hot and cold basin taps in the en suite come from the same pipes (I installed them) and the cold cleary comes out much faster than the hot.

someone has sugested - would a 'non return valve' on the hot water under the bath help to solve the problem? Because the hot water couldn't be forced back down the pipe and would have to come out with the cold?

Or do I need a seperate mixer shower like in the en suite? If so, what do I need to look for? I don't want to spend £200+ and all the time plumbing it in if I get the same problem.

 

[ChrisR]

If you can easily stop the flow from a tap with your thumb, it isn't from the mains.

If you have mains cold and tank-fed (ie gravity) hot then most thermostatic mixers can't cope. NO manual mixer will give you mixed water without problems.
You need to reduce the pressure of the cold, preferably my supplying it from the same cW tank as advised. You can try pressure reducing valves, pressure equalising valves etc, but the results are not generally good.

SO you have to use 2 x gravity supplies. If not enough pressure, you have to pump them both, but with such a low static head, as you have, that is likely to give problems too.

 

[MrMoo123]

I can't stem the flow from the cold with my thumb - it really does have a high pressure.

I appreciate what your telling me but one fact remains - the en suite shower works fine from the same feeds as the bathroom.

Therefore it must be that if I bought a similar mixer shower as I have in the en suite then surely it will work the same?

And what of the non return valve mentioned above? No good?

 

[ChrisR]

Therefore it must be that if I bought a similar mixer shower as I have in the en suite then surely it will work the same?

NO.
I just answered that.



NRV's won't help water mix.

 

[cider]

some showers and taps have backflow devices fitted and thermostatic valves can compensate for unballanced pressures up to a point.
If your tank is called a showermax it would indicate it is designed to give a high pressure shower outlet. the fact it has a cold storage on top would suggest the rest of the hot outlets are low pressure.
is the hot water pressure greater at the ensuite then anywhere else in the house?

 

[MrMoo123]

Ok I'm gonna pull up a few floor boards tomorrow and figure it out once and for all - I just ran the hot tap in the en suite which im certain is off the same feed as the shower in there and the same pipe goes red hot in the airing cupboard as does when you turn the hot tap on in the bathroom but it was 3 years ago that I plumbed that in so its not impossible that there is another pipe in there that purely feeds the shower and would make a lot of sense.

If that turns out to be the case what are my options guys? Would I only be able to re-plumb from this 'shower pipe' or would you suggest electric or maybe a power shower? I know electrics don't tend to give off that great pressure but its gotta be better then what I have now.

Would a power shower work on my setup?

 

[cider]

u cant hava a power shower cus u have no storage. no needt to lift floor just see if a seperate pipe from cylinder gets hot when running existing shower it will be a pipe exiting cylinder top side of hot section also to proove what im trying to tell you does the hot from ensuite shower stop immeadiately when you turn off cold mains when rest of hot still runs? sorry for poor typing but late on sat!

 

[MrMoo123]

Ok correct you are - there is another hot pipe that feeds the en suite shower. Thanks for your help.

So I guess that leaves me 2 options?

1) connect up a feed to this pipe and route it to the bathroom to use as hot water in there - will this effect performance of say both showers if they are both switched on at the same time? Also will I be able to use this to fill the bath with or will it be better to get a seperate shower mixer from the bath taps and feed it only to that leaving the bath on the current water supply?

2) Electric Shower. Am I right in asuming i've got to take the electrics from the fuse box for this in which case an electrician would be needed?

 

[cider]

1) connect up a feed to this pipe and route it to the bathroom to use as hot water in there - will this effect performance of say both showers if they are both switched on at the same time? Also will I be able to use this to fill the bath with or will it be better to get a seperate shower mixer from the bath taps and feed it only to that leaving the bath on the current water supply?

Not ideal as would affect performance of both showers and def not suitable for filling bath as the high pressure coil in the cylinder is drawing alot of heat from the store (esp if its electricaly heated).

2) Electric Shower. Am I right in asuming i've got to take the electrics from the fuse box for this in which case an electrician would be needed?[/quote]

yes !

 

[MrMoo123]

Went with Option 1 as in the end it came down to what was going to cost lest / take the least time.

My fuse box is at the other end of the house and downstairs - to get an electric cable from here would have caused total chaos!

Fed up into the loft and back down into the bathroom. I'm going to use this feed purely for a seperate shower mixer so won't be used to fill the bath.

The pressure is good, much, much better. Although not quite as good as the cold i'm hoping that a decent shower mixer will help me out here, if not im screwed. At the end of the day its probably only going about a foot max higher then it does in the en suite. I pray it doesn't make too much difference.

Ran the shower in the en suite at the same time and it didn't make that much different in pressure - although I agree its likely affect temperature when both ran at the same time, we will see. However the chances of us having both on at the same time are remote (perhaps once or twice a year) so when faced with that possibility or that of having my entire house pulled apart to feed an electric shower, I went with that.

Thanks for all your help.