monoblock, washer and hot isolation valve

[rabu]

Hi, Im about to fit a monoblock kitchen mixer, after looking at the 2 washers supplied, there is one narrower and smaller diamiter washer and one larger one looked at tap and saw a recess on base, the small washer fits in this perfect, so is that the way they go, small one under tap and larger one between horseshoe and under sink? also looking at the isolation valves under sink, the cold one looks ok, but hot one starting to look manky and worn so was going to replace this with a full bore valve dont really want to drain system to swap this over, (have to turn of outside on mains, drain down..refill primatic cylinder...) since the hot pressure isnt that high would this be "ok" to get the old valve off and new one on, (seen some plumbers do it with not that much water all over the place) with the pipe still live? any help or advise is welcome, thanks.

 

[sdsparks]

Dont forget you need to install back flow prevention valves if the hot and cold are mixing in the block!

 

[WaterTight]

Horse-shoe shaped washer goes with identical shaped metal washer, underneath sink, between basin and metal washer. You may receive spare small circular washer for flexi connectors. They look more like o-rings (not flat.) A Larger o-ring type washer may also be included which fits in groove under tap base to protect basin surface and make water seal when tightening. I'd smear a bit of LSX or silicone round the rap hole anyway before fitting to be sure no water goes down.

Screw the monobloc securing screw and one (or two if they'll fit) flexi or rigid tail into base before putting through hole to make life easier. You don't have to have a monobloc spanner set to tighten the nut but it can be very hard if you don't have one. Buy a set that has a good range of sizes (6 sizes over 4 spanners for instance)

Does the isolation valve shut off? If it is just manky, give it a good hard clean with an abrasive pad. Chances are it's just dirty and encrusted. If it won't work you will need to drain water. If you turn off a gate-valve or other isolation on cold feed to cylinder it may make vacuum where you don't need to drain anything. But failing that you won't drain the cylinder anyway. The water will just drain up to the draw-off point at the top of clyinder.