Recently I've found that in the morning my second floor bathroom sink will
produce warm, almost hot water from the cold tap for about 15 sec. in the
I'm thinking - "this is GREAT, the city is piping us out hot water! - this
will sure help with my New England winter heating bills!". then I woke up...
It's an old sink with separate taps, no mixing valve.
Is this an indication of another mixing valve failing? My shower has a temp
regulating mixing valve which seems to be function properly - is that the
likely culprit? Would hot water run back into teh cold line and come out the
cold side 5 feet away? - WHy? the pressure is the same in the hot and cold
lines, isn't it?
I've never heard of this symptom - any one else??
My bet is you have someplace where it is mixing in the basement. Do
you have something that uses hot and cold water there? Maybe a leaking
washing machine valve? It could also be a bad dip tube in the water
Hot water will naturally rise in the piping so any interface of hot
and cold water will show up in the 2d floor bathroom.
"Recently" as in "since you turned the furnace on for the season", I'll bet...
My guess is that the supply lines to that sink pass close to a heat source.
Does your house by any chance have hot water or steam heat? If so, ten-to-one
IMO that your supply lines (or the cold one, at least) run right next to a
radiator in the next room.
Doug Miller (alphageek at milmac dot com)
When no water is being drawn, the hot water pressure can rise above the
supply pressure due to expansion in the heater along with a no-return check
valve in the supply line. Expansion can back up the hot water into the cold
lines if you have a regulator on the water supply and no functional
expansion chamber. This can sometimes open the relief valve on the water
heater. Thermo-syphoning can also occur between hot and cold water lines,
particularly with mixing valves which can develop internal leaks between the
hot and cold supplies without noticeable leaking out the spout. Not real
common but also not real rare.
You probably have some hot and cold water pipes running alongside and in
contact with each other causing the hot water pipe to transfer heat to
the cold water pipe, heating the water inside.
This is quite commonly caused by internal leakage in any one of many kinds
of single handle faucets. It can be aggravated by expansion of hot water in
the heater where there is a check valve or regulator to prevent backup of
expanding hot water into the supply. Sometimes hot water will back up into
the cold water line feeding the heater, past where the cold water feeds
somewhere else. It is often possible to find the source of the problem by
careful feeling of the cold water lines.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.