Trivial question about hot water supply

OrionRed · Apr 27, 2011

I am having trouble figuring out why, when you turn on a distant faucet, the water SLOWLY gets hot. It seems to me that it should be cold...cold...cold...hot.

It doesn't seem like the copper pipe should cool it off that much between the tank my bathroom. It's maybe 50 feet of run.

So...is the cold water in the pipe also mixing with the hot water running towards the faucet, or is the copper taking all that heat?

Like I said, it's trivial. But now that I've noticed it, I can't stop thinking about it.

LLigetfa · Apr 27, 2011

OrionRed said:
...or is the copper taking all that heat?

Ja, the copper is soaking up the heat.

Sponsor · 2022-01-29T12:20:58-0800

OrionRed · Apr 27, 2011

Mythbusters time!

Makes me want to set up some experiments and see what I get.

LLigetfa · Apr 27, 2011

There are two physical properties to factor. One is the thermal mass of copper and the other is the thermal conductivity of copper to the surrounding air. Copper is quite good at both. The large solder irons are made of copper because they can absorb a lot of heat. Copper is used in heat exchangers such as a heat pipe inside a computer.

Gary Swart · Apr 27, 2011

This is why many of use like a recirculating system...instant hot water.

OrionRed · Apr 28, 2011

Thank you both for answering. If nothing else, I could turn this into a science fair project.

hj · Apr 28, 2011

It is also the reason why hot water pipes should be insulated, to retain the heat. The copper does NOT "soak up the heat" it transfers it from the water to the surrounding air. And it occurs in direct proportion to the difference in temperature between the water and the air. The cooler the air, the longer it will take for the water to get "hot".

Jerome2877 · Apr 28, 2011

Another reason for warm water before hot is heat migration from the tank to the outlet pipe. If you touch the outlet pipe it will be warm for a couple feet.

hj · Apr 29, 2011

quote; Another reason for warm water before hot is heat migration from the tank to the outlet pipe.

As stated previously, it is NOT another reason, it is the ONLY reason why it happens.

Jerome2877 · Apr 29, 2011

No there are 2 things going on, 1 is the heat loss while the tap is open and running through the copper, the other (what I'm talking about) is the migration of hot water into the outlet pipe while there is no water being used. This will cause warm before hot as well.

OrionRed · Apr 29, 2011

So the water in the tank circulates a little bit up into the outlet pipe? Is it actually moving some water with convection, or is it the copper conducting heat out of the tank? Or both?

hj · Apr 30, 2011

Convection is moving the heat out of the tank, but that is merely accelerating the movement of the hot water to the faucet when it is opened. The convection ONLY occurs in the piping that is rising from the heater. As soon as the piping turns downward the convection stops.

Trivial question about hot water supply

Users who are viewing this thread

OrionRed

New Member

LLigetfa

DIYer, not in the trades

Sponsor

Paid Advertisement

OrionRed

New Member

LLigetfa

DIYer, not in the trades

Gary Swart

In the Trades

OrionRed

New Member

hj

Master Plumber

Jerome2877

In the Trades

hj

Master Plumber

Jerome2877

In the Trades

OrionRed

New Member

hj

Master Plumber

Similar threads