My
first thought is that there is some type of cross connection. It could
be at the washing machine. Look for a cross connection somewhere.
Isolate the washing machine, and see if that helps. Then try to work
at isolating any fixtures that share hot and cold. Close the valves
under the sinks, try to cut in valves at the showers etc. There is
always an answer.
Answer: You have a by-pass connecting the cold water line
to the hot water line. Could be a faucet, washing machine, hand
sprayer with a shut off and the faucet is left open, or a potable
dishwasher . You could check for a migration of hot water from the
water heater to the by-pass. Or shut off one by one and check if hot
water flows. Water takes the least resistant path.
Answer: Has the water flow changed on the DHW side in the
last two months? Has anything else changed besides a loss of hot
water?
Answer: Your problem sounds as if you may have a cross
connection between the hot and cold water line. This is a common
occurrence when there is a remote wand shower head that is kept in the
off position at the shower arm with the hot and cold water valves left
on.
It could also be caused by a cross connection at
the automatic clothes washer. Make sure that there are no cross
connections as explained above by making sure that the hot and cold
water lines are kept closed at the clothes washer, and any showers
with remote hand held wands.
Answer: Do they have copper pipes or galvanized pipes, or a
combination of both? I have seen dielectric unions that were so badly
corroded shut, that the hot water would not come out. I even have one
sitting on my shelf that has a large rock jammed in it, completely
blocking the flow! Check the aerators, dip tube. One more thing to
check: Is there a gate valve someone has shut off, the stems sometimes
break off (handle just spins) and you can’t turn it back on!
Answer: Sounds like a mixing problem. A simple test: Turn
off the feed at the tank and turn on a hot water tap. If water flows
without stopping, cold water is getting into the hot water system. If
the taps in your home can be isolated, turn off the taps and the
shut-offs until the water stops. That is where it is mixing. Repair or
replace. Don't forget the washing machine or any place that has both
hot and cold water. Murphy's law states that the tap you turn on is
the problem, but you won't know that until you try all the rest.
If no water comes out when you try the
aforementioned test, I would check the dip tube on the inlet side of
the hot water tank. If it has cracked or broken off, it will cool the
tank water quickly. Call in a pro to check this one as you will have
to remove the inlet piping to the tank.
Answer: Also might be a tempering valve feeding a toilet
leaking by.
Answer: Had a similar problem at an apartment house earlier
this year. Tenants started complaining of no DHW. I discovered a
cross-connect that was pumping cold into the hot. Took a good deal of
snooping to find it. When you run the hot water, place your hands on
hot and cold pipes at water heater. Are they both cold or is one hot
and one cold? Can you follow the pipes from the heater or do they go
into the walls? If you turn off the cold valve under the sinks does
anything change? The washer?
Answer: Got any Moen single handle faucets or valves? They
have been know to allow some cross over when the O-rings wear or go
bad. Had to troubleshoot one of those in a hotel once.
Answer: In older homes, the piping was often done in
galvanized pipe. The piping tends to corrode badly, especially on the
hot water side. It is possible that the corrosion slowly blocked off a
branch section of your hot water piping that fed those areas. Look or
have someone look to see if your domestic water pipes are galvanized
(even just in that area-sometimes in the older days they would switch
materials midstream for no apparent reason).
