dcv

Hi I want to replace my outside tap and pipework as the old one doesn't have a Double check valve (inside or out). I have purchased A DCV and isolator, but do I need a drain-cock on the inside? also is it - isolation valve then DCV?

Renovating the kitchen at the moment and thought it was a good opportunity to rip out the old water pipes that had seen better days and fit fresh ones. My main water comes up from under the stairs so I’ve fitted a pegler stopcock before it heads into the kitchen. There’s no sign of a DCV before...