My bathroom pipes (facing the prevailing winds) froze last night. I noticed
when I was trying to figure the extent of the damage that when I turned on
the cold water tap on the lav, the other lav and the shower BOTH went on!

In detail:

I turned on the hot water taps of both lavs and the shower. A few drips came
out, then ceased. Given the temps, I just knew we had a frozen pipe nearby
under the house. This has happened before and always thawed.

To check, I turned on the cold water tap on the right hand lav. The HOT
water taps of the left hand lav and the shower immediately started flowing
full force! -- with icy water. Never did warm up.

I repeated using the lefthand lav cold water tap. Same thing: the righthand
lav and shower both flowed with cold water. The only tap that was on in both
was the HOT water tap.

I repeated with the shower tap. Nothing happened. The cold water tap in the
shower worked, but didn't trigger the HOT water taps of the lavs.

The lavs are further out from the main and from the hot water heater by about
five feet, against an exterior wall facing the prevailing winds. The shower
is interior, accessible by a panel in an interior wall.

Why on earth does turning on a cold water tap trigger cold water flow in a
hot water tap??

btw, the pipes had not burst. I set a heater under the house to thaw the
pipes and it worked well. All is back to normal now, with hot water taps
providing hot water in all three locations and cold water not triggering flow
in any other faucet.

Is my plumbing possessed??

Katherine Bryce
Santa Fe NM USA