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Andy Hill
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Samiel wrote:
On Tue, 11 Jan 2005 11:40:16 -0700, Andy Hill
How much airflow are we talking about here? If you put something really light
(like, say, tissue or toilet paper) over the drain, can you see the paper being
moved by the air? A little? A lot? Is the airflow *into* the drain, or *ut
of*the drain?

I put a single sheet of TP over the drain and I could see some little
puffs of air affecting the TP. So, there's definitely air going in or
out of the sink drain.

Is it possible that for some reason, when the heater/ac unit is
running that the drain is trying to pull air into itself? Maybe what
I hear is a tiny bit of water being pulled in and then let go?

OK, I'll have to go into seriously left-field mode here, since I really can't
think of any logical reason why an electric furnace could affect the water in
the sink trap.

(1) Maybe the air conditioner condenser drain (assuming you have central air) is
plumbed into the waste stack near where the sink is plumbed into the waste
stack, the trap in the condenser drain has dried up, and there is enough air
being blown into the condenser drain that it's backing through the trap in the

(2) Maybe the furnace return isn't sized correctly relative to the number of
vents, and you're getting so much back pressure in the house (or otherwise) that
air is having to be sunk or sourced through the trap into/out of the vent stack.

Frankly, both of these are seriously far fetched, IMHO. Since the house is
pretty new, I'd probably just have the builder come out, show him the problem,
and let *him* figure it out.