shower on ground floor off house

[young plum]

Hi i am installing a bathroom suite next week for college work.
I am doing it at a friends house they have an electric shower now but they want a thermostsic bar mixer.
They dont have a combi they have a cold water cistern in the attic and hot waer tank in airing cupboard next to it.
I told them it would be allot of work with haveing to go into the attic and dropping a cld water pipe down to bottom floor.
Am I allowed to tee into the hot and cold bathroom taps as some people say yes and others no
Please any advice would be appreciated

 

[Slugbabydotcom]

If you follow the installation instructions the job will be right.
If you don't it wont.

 

[ChrisR]

That's true, but sometimes it work fine. Depends on flow rates, pipe configurations etc. Sometimes it's worth a try, if it's that much easier than the "proper" way.
If you use a pump, risks are things like sucking water and air up other taps, wc cisterns, vent etc, and starvation of the shower when another tap is used. If you don't use a pump then those problems will be much less. Worth using a thermostatic mixer for the variability you would expect when other people use taps.
SO if you warn the customer up front...