Anyone tell me which pipes do what on the piccy....


Had the usual probs.. Want hot water but get luke warm but radiators get hot.. Ive had off and looked at diaphram but seemed fine, Just wondered how it worked to see if i could cure by say stretching spring etc. Can get new one but it dont look bad so wanted to see if could fix this first.

Its on a wanky Ravenheat littlestar, The smooth groove but below the 2nd fitting on pic carries what seems like a flow swich which clips on if that helps..