Bathroom refit being planned. Have bough a wall mounted bath mixer tap with hand shower attachment (http://www.grohe.co.uk/en_gb/concett...-32212001.html or http://goo.gl/WE1B5C).

Whilst I was waiting for Grohe to confirm which were the cold and hot inlets (I'd assumed the right one was cold as per usual but its best not to assume, and nothing in the installation instructions), I decided to just blow into the inlets and move the tap from hot to cold (cold inlet is on the right by the way). I've found that whilst there is a non return valve in the shower outlet, there is nothing to stop flow between hot and cold inlets.

The question is, given I have a Megafow system with hot water being delivered at close to mains pressure, is there any need for me to insert non return valves into the hot/cold feeds to the mixer? The same H/C feed will be supplying a (thermostatic) shower in the same room but I can't see a time where we'd be using both shower and bath.