From: patter@dasher.uucp (24224-guthrie)
Subject: Re: drain vents might be
Reply-To: patter@dasher.cc.bellcore.com
Organization: Bellcore, Livingston, NJ
Distribution: misc
Date: Sun, 26 Jul 92 18:27:16 GMT

In article <1992Jul25.1282.9351@execnet> "ron kulick" <ron.kulick@execnet.com> writes:
>       In article <1992Jul22.000325.22946@porthos.cc.bellcore.com>
>               patter@dasher.uucp (24224-guthrie) writes...
>
>>Most plumbing codes require that each bathroom be vented separately.
>
>The codes require that each "fixture" be vented. Fixtures are defined as
>sinks, tubs, floor drains, water closets, urinals, etc.

As of 1980, neither Knoxville, Tennessee nor the various Atlanta, Georgia
codes required this. Fixtures that are close enough together may share
a common vent. In addition, the drain line from an upstairs room may serve
as the vent for lower floor fixtures.

>>The vents are usually two or three inch plumbing pipe run straight up
>>through the roof.
>
>The vent lines in the walls are usually 1.5" or 2", which connect
>horizontally with a slight upward pitch into a 4" vent stack, which in
>turn goes through the roof.

Not in any house I've worked on. Invariably there is a 2" or 3" pipe
extending vertically from the highest main drain (usually a sink).

>>I think you may have two problems, though, because the vent situation
>>won't normally cause *all* the sinks to drain slowly.
>
>If the vent stack is clogged at a point higher than the highest fixture
>all the fixtures will drain slowly.

*IF* he has a single vent stack.

>>Oh - one more thing. If you have more bathrooms than vents, this is
>>not good.
>
>I don't know where you get your information concerning plumbing codes or
>practices, but maybe you might want to double check them.

I "get them" from over 15 years experience in the commercial construction
trades.

In that line, I was thinking of ranch style houses. Examples of venting
situations (all legal):

1. My mother's house is a ranch with crawl space. I've seen the plumbing.
   It has one bathroom at one end, two baths at the other, and a kitchen
   in the middle. It has three 2" stacks. One extends from the sink drain
   of one bathroom and serves as the vent for all three fixtures. Another
   extends from the sink drain of the other two baths (they both share the
   same drain) and it vents all six fixtures there. The third one vents the
   kitchen sink. All drain and vent plumbing is cast iron. The house was
   built in 1963. Tennessee code.
2. My house was built in 1959. It had a laundry room, kitchen, full bath
   and half bath. The half bath is located over 20' from the main drain
   line, which is 6" cast iron. The remaining fixtures are all within a
   few feet of this drain. There was one 2" vent extending from the top
   of this drain line just above the point that the second floor bathroom
   sink drain enters the line. In effect, the laundry room was vented through
   the kitchen sink main drain, which was vented through the bathtub main
   drain, which was vented through the toilet main drain, which was vented
   through the bathroom sink main drain, which was the only vented fixture.
   Astute readers will notice that this arrangement leaves the half bath
   unvented! In addition to a "snuffling" noise, you could watch the water
   in the toilet bowl make the noise if you ran the water in the sink next
   to it. The room has its own vent now. This was New Jersey code.
3. My brother's house has a laundry room, kitchen, full bath and half bath.
   The rooms are "stacked". All fixtures are within ten feet of the main
   drain, which they all share. The 3" vent line extends upwards from the
   top of this drain stack and vents all fixtures. This house was built in
   the 30s. The half-bath toilet has been known to produce a "snuffling"
   noise when other fixtures drain. This was New Jersey code.

I could go on, since I've done the framing for a few plumbing jobs, but
enough. You will notice that neither of the first two houses are
particularly old, and NONE of the three have anything like separate vents
for each fixture.

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