A very common cause of this is a single handle faucet which leaks internally
between the hot and cold connections. Feeling of the supply pipes will
detect this. A check valve or regulator in the cold water feed without an
expansion tank at the heater will also do it.
Don Young

"Pop Rivet" wrote in message
news

"mike" wrote in message
om...
I manage the facilities for a 100 year old hotel turned
into a
school...in our big commercial kitchen, when you turn on
the cold
water in the morning at the sinks you get 30 seconds of
very hot water
coming out...thn the cold comes...anybody got any clever
ideas on how
to figure out where it is coming from...I already know I
can hire a
plumber who may spend hours tracking it (at $90 per
hour)...I am
looking for a do-it-yourself solution.

Many thanks for any help.

Mike

I don't think proximity of the hot/cold pipes would result
in water as hot as you seem to indicate, but it's possible.
Especially if they happen to be wrapped in the same
insulation somewhere along the line.

Check around the plant equipment: water heater, boiler,
etc., for valve arrangements that could tie hot/cold water
together. If it's not proximity heating, which I don't
think it is, the somewher along the line there must be
someplace where valving or even a stupid plumbing mistake
let the two cross somehow where there is a slow running
mixing.
What's the possibility that all the air-traps and/or
tanks are waterlogged and during nonuse, heating of the
water causes water th back up, and when it comes forward,
comes out the cold water pipe?
Try running the hot water first, then the cold water
after. If the cold isn't hot then, it's pretty likely a
backup around the heater/boiler, whatever you have.

Pop