" wrote:

If he really does have a reverse airflow through his flue caused
by his roof fan, then a chimney liner is going to do ****-all to
help that situation.

Excuse me, ignoramus, but first, if you look at that in context,
which you did not, the problem I was specifically referring
to the chimney liner solving is the case where the chimney
is too large for the water heater.

You can't say that his chimney is too large unless you know if he lives
in a northern climate and if he has a high-efficiency furnace.

In a northern climate, you can have condensation inside the chimney if
there is not enough total combustion flow (furnace + water heater).
Normally for a regular furnace, it's putting out enough exhaust to keep
a good convective heat flow going and "help" the water heater flue stack
flow.

In the summer, there really isin't a problem with needed help from the
furnace (which you won't get anyways because the furnace doesn't run in
the summer). The water heater exhaust flow should have no problem
getting up and out the chimney in the summer. Now if you have a reverse
air-flow in the chimney, then nothing you can do to the chimney
(including using a liner) is going to help with that.

So unless you know what type of furnace he has, and just how cold it
gets where he lives, then you can't say that he *needs* a liner for his
water heater exhaust.

And like I said before, even in cold climates it's standard to have a
non-lined chimney and have furnace and water-heater exhaust run
passively up and out the chimney. It's only when you have a
high-efficiency furnace do you start to look at using a draft motor or a
liner to help the water-heater exhaust.

And second, having the flue correctly sized to the appliance
helps create the correct draft.

**** the draft, and the sizing. This isn't rocket science.

When you've got something creating a negative pressure in the house,
causing reverse air-flow through the water heater flue, then you put
down your books and graphs and tables and you fix the reverse air
problem.

If the flue is sized correctly the hot gas stays hot and rises.

Again, you're completely disregarding the whole point that started this
thread.

This boob thinks that he's getting a breeze flowing into his water
heater exhast flue and blowing out a match that he holds against the
draft intake vent (presumably the gap between the water heater and the
flue intake above it).

None of your correctly-sized **** is going to make that breeze go away.