to connect something {e.g. toilet, bath, washing machine} to a water supply
We've had the dishwasher delivered but we're waiting to have it plumbed in.
phraseplumb in plumb in sth • plumb sth in to connect a bath, toilet, washing machine etc to the water supply: The Whirlpool dishwasher is easy to plumb in - you can do it yourself.Once the sink has been plumbed in, a silicone sealant is used around the edge to make it watertight.