Running out of hot water in showers while getting enough in faucets

[David Williams]

-> As far as the faucets in the bathrooms, kitchen, dishwasher etc. there
-> is a good supply of hot water.
-> However, the hot water runs out in the showers within the first five
-> minutes. We have had 3 plumbers look at the problem so far and none of
-> them are able to resolve the problem.
-> We put in a new mixing valve at the boiler, this made it a little
-> better than before when we were getting hot water only for a couple of
-> minutes.
-> What is puzzling is that it is happening only at the showers. It is
-> also happening at all the 3 showers in the 3 bathrooms.

You imply that you have hot water at the faucets at the same time as
there is no hot water in the showers. Right?

The only explanation I can think of is that the hot water to the
showers leaves the tank from a different, and lower, outlet pipe than
the water to the faucets. So when you run the showers, cold water goes
into the bottom of the tank, and soon gets up to the level where the
outlet to the showers is. So the showers go cold, even though there's
still plenty of hot water in the upper part of the tank.

But why would anyone rig up things that way, unless he was trying to
discourage people from taking long showers?

dow

 

[Gordon]

[email protected] (David Williams) wrote in

-> As far as the faucets in the bathrooms, kitchen, dishwasher etc.
there -> is a good supply of hot water.
-> However, the hot water runs out in the showers within the first
five -> minutes. We have had 3 plumbers look at the problem so far and
none of -> them are able to resolve the problem.
-> We put in a new mixing valve at the boiler, this made it a little
-> better than before when we were getting hot water only for a couple
of -> minutes.
-> What is puzzling is that it is happening only at the showers. It is
-> also happening at all the 3 showers in the 3 bathrooms.

You imply that you have hot water at the faucets at the same time as
there is no hot water in the showers. Right?

The only explanation I can think of is that the hot water to the
showers leaves the tank from a different, and lower, outlet pipe than
the water to the faucets. So when you run the showers, cold water goes
into the bottom of the tank, and soon gets up to the level where the
outlet to the showers is. So the showers go cold, even though there's
still plenty of hot water in the upper part of the tank.

But why would anyone rig up things that way, unless he was trying to
discourage people from taking long showers?

dow

No, It's because there is still hot water in the pipes going to the
faucet. If the faucet was run long enough it too would run out
of hot water.

Usually the problem with a shower running out of hot water is due
to the lower element of the hot water heater being burnt out. Only
the top element is working and is heating the top of the tank. the
rest of the tank is full of cold water. It doesn't take long for a
shower to exhust the limited supply of hot water.

It could also be due to the dip tube failing. This was a problem
a few yeas ago.

 

[Steve Spence]

I had a similar issue. It was a bad faucet stem seal that slowed the hot
water as it heated up.

 

[Ecnerwal]

Usually the problem with a shower running out of hot water is due
to the lower element of the hot water heater being burnt out. Only
the top element is working and is heating the top of the tank. the
rest of the tank is full of cold water. It doesn't take long for a
shower to exhust the limited supply of hot water.

It could also be due to the dip tube failing. This was a problem
a few yeas ago.

Neither of which has anything to do with a oil-fired-boiler with
hot-water coil system such as the original poster has. No tank, no dip
tube, no element.