hello. had a electric shower for ages now. lookin at getting a consealed mixer shower. not really sure if this is ok cause i have a emersion hot water tank with the cold water tank sat on top of it ( one unit ) so will be gravity fed, the outlet from this tank (hot water out 22mm) will be lower than the shower head by approx 2 foot. i have no cold water tank in the loft. do i need a pump and i dont understand this essex type valve ? if i can use this type of valve whats the best way to pipe up etc. thanks