Smelly household water

[DebtMan]

In the last couple of weeks, my girlfriend and I replaced her kitchen.

We couldn't turn off the water in the house as the stop cocks were jammed solid, so we turned off the main stop cock in the kitchen and then drained the system and water tanks.

Now we are getting a stale water smell mainly in the hot water, but also to some degree in the cold too.

Any ideas??

Thanks