Plumbing vents

I recently spent a few days helping a friend install vents in the plumbing drain system in a log house he's building. I'd never really thought about venting, so when I got home I checked out my venting and discovered that I don't have any. This place was renovated, or being rerenovated, by a couple that went broke and we bought it from the bank so I don't know what the plan was. There's about 35' of 4" ID pipe to the outside wall and on to the septic tank. All the drains come together within 5' of the other end of the pipe. I can easily put a vent pipe through an outside wall but I'm wondering if it should be at the septic tank end or the other end. Brian, in Cedar
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Brian Barnson wrote:

No vent stack thru the roof??
See this excellent article for an understanding of the venting function and principles: http://www.pmengineer.com/CDA/ArticleInformation/features/BNP__Features__Item/0,2732,101269,00.html
Jim
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One vent stack through the roof, but it's part of the old black iron system which is disconnected. The new plastic system is sans vent.

http://www.pmengineer.com/CDA/ArticleInformation/features/BNP__Features__Item/0,2732,101269,00.html
Thanks Jim, that is a good article. I'd been leaning towards venting the tank end, thinking that a draining tub or a flush was pushing air that had nowhere to go. It looks like it's the other end near the drains that needs venting. Care to guess which end involves lying on my back in the crawl space? Brian, in Cedar
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On Mon, 30 Aug 2004 20:36:52 GMT, "Brian Barnson"

Why not just get some fernco couplings and connect to that cast iron stack. It might not be perfect, but it should work. I used to live in a house that only had a vent in the center of the whole pipe system, just before going to the septic tank. It did not have individual vents at each sink, etc. The sinks gurgled, but otherwise everything worked.
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I don't know how long you have lived there but I would say you're vented somewhere. If the septic tank system wasn't vented it would backup. I've seen this happen. I had a house build once and one of the subcontractors didn't put a trap in the basement shower drain. I was getting odors in the shower. The primary contractor didn't want to tear up the concrete shower floor. He went to the septic line just outside the house and put a trap between the house and the septic tank. When I ask how the system would be vented he said it would vent through the fielding. I thought this was wrong but I let him put the trap in. Within a week I had raw sewage in my basement shower. I went out dug up the trap and drilled a hole into it on the tank side. You could hear air rush out, then the sewage ran down to the tank. I put a tee on the hole I drilled, ran it above ground level and covered up the trap. No more trouble. So if you are not vented at all you should be having REAL problems. Some 'handymen' run vents into an attic and let it end there. Not code, and not a good idea. If you're in doubt run a vent line. You're venting the septic tank, so no traps can be between the tank and the vent. If the system was installed correctly each toilet would be vented (to a primary line). If not you system could vacuum lock and no water would move.

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I've looked pretty thoroughly and I can't see any vents. There could be some inside walls that end in the attic, but I haven't seen any up there. The only time it acts up is if 2 large volume things (toilet and tub, toilet and washing machine) are draining at the same time. Then the toilet lacks enthusiasm and needs to be reflushed later. Normally (one drain at a time) the drain water seems to run downhill adequately. No smell of sewage anywhere. I'm thinking the previous owner didn't know about venting. Brian
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