hot water tap washer or dishwasher

Hi, I will assume that you have available both hot and cold water feeds (but only one of each). Your choice could be dependant upon several factors. If you have occasions to use coldwash cycles in your clothes washer and does the instruction manual permit hot water connection to the cold intake. Is your hotwater delivered directly from a Combi-boiler, this would be impacted when taps / showers / clothes washer / dishwasher are used concurrently. If you are interested in shortening the running cycles of the machines by delivering pre-heated water, then this may be effective but I beleive the cost of the water heating would be equitable between the two methods.

Neither, why do you want to?

If you got 2 water connection, (hot and cold) they were installed few years ago, probably to connect to old type WM. Nowadays the Washing Machine and dishwasher are to be connected to cold water supply only end eventually water is heated by an electrical resistance inside the appliance. Just ignore or remove the hot water valve and connect a second service valve from the cold water pipe. Tiziano