hot water coming out of cold water taps

Hi...I am the Facilities guy at a 100 year old school (it was once a hotel many years ago)...I don't have much plumbing experience...every so often we get hot water coming out of the cold water taps...usually it is lukewarm, but lately it has been very hot.
Possibly, this latest problem dates from the time 6 months ago when we had our dishwashing room done over...the sinks where it happens most back up to the wall that has the dishroom sinks.
We have pretty good plumbing drawings, altho some are 30 years old.
Any ideas on how we can start to track down where the problem is?
Also, I don't mind hiring a pro, but I would like some ideas on how to start him/her off in the most efficient way.
Thanks for any help,
Yours truly,
Getting Steamed
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"mike"
Don't worry about not having much experience in plumbing, but asking questions on this newsgroup. We live to serve folks in situations like this...
Somewhere there's a cross connection between the hot and cold water pipes. What this means is that when you open the cold side of a faucet, it draws out of the hot pipes too.
My first guess is that in the dishwasher room, there's probably a rinse sink with one of those faucets that has a long spray head on a springy type of spout. Often, this faucet has both hot and cold on at the same time. These faucets have built in backflow preventers (sometimes a little ball under the hot and cold stems). If these fail, then when you use the faucet in a nearby sink, water will flow from the hot at the rinse sink, through the faucet and into the cold pipes leading to the other sink.
As an experiment, close the rinse sink faucet at the hot and cold handles, and see if the problem clears up. If the problem persists, there are other suspects (like washing machines). Write back with more info.
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I'm a plumber that works at an old school also. You may have an old faucet such as and american standard,symon or water saver that has a round gasket that seperate the hot and cold in one chamber. Turn on the cold water of the offending valve and let it run. Then walk around and feel all other valves. the warm ones are you culperits. rebuild them.
Hope It works for you
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