Wet Venting (plumbing)
 

Anybody know the pros and cons? I did part of a bathroom in a recently purchased (foreclosed) home up in the Oakland Hills. Expensive neighborhood, the house looks good but it's a serious piece of work.

Exterior and framing OK, but it has a blue glazed tile roof, shed roof all around, that is, no gable ends. A tad off the main point but this was the beginning of my drama with the house as she wanted bath vents in the two upstairs baths. 4 baths in this upscale house and only the guest toilet off the living room has a vent fan and it vents down and out the crawl space, if not merely into it.

Much of the interior work was done by the original owner who barely knew what he was doing. Long story. House is only 7 years old, BTW.

Putting a roof jack on a tile roof is bound to be some $$, I don't do it, that's for certain. On a shingle roof -- cedar or composition -- I'd have put in a roof jack last week. So I ran soffit vents. Not ideal and they're not working that well. Poor air flow. And it's all my fault of course. They do pull air into the bathroom from the adjacent rooms so stink and steam will not waft into the rest of the house.

On the wet vent, she wanted a wall mount vanity in the mast. bath with 2 sinks. No room behind the vanity for the plumbing, so I had to open the wall and move the drain and supply line for one sink (only about 8 inches to the left) and make a new drain and supply about 4 feet to the left.

Over almost exactly where the far left drain needed to be was an ABS 2" vent coming up from the bath in the au pair quarters on the bottom floor. It's not code but word is wet vents almost always work out OK, unless you have girls' soccer teams using both bathrooms as a dressing room at the same time (be still my foolish heart).

And that's what I did. No problem so far, but don't get me started -- this job was (is) a trip.

I agree........a wet vent on a vanity generally poses no issues.

Oh good, a little more affirmation helps. I'm starting to get the part about why plumbers pay major $$ for liability insurance.

A bit of irony in this job -- the owner is an insurance co. executive, and here she is using help off of craigslist, paying cash, so she has to know she's saving $$ by using low bidders. Part of the reason the large firms are expensive is the large insurance premiums they have to pay.

So this lady makes decent money selling insurance, but she doesn't want to have to bear the expense of it in her private dealings. She's not rich, I don't reckon, but she does drive a new Boxster and the house couldn't have been cheap -- it's got major view action and this neighborhood is spendy.

You're typically running 1 1/2" for the vanity from the wall to the 2" or 3" drain line. It's virtually impossible to fill that line more than 1/2 way due to the limitations of the vanity drain..........it won't flow enough water. So, there is always the upper part of the line to allow air to return from the main vent.

If you somehow managed to fill the 1 1/2" line.........then, you'd have drainage issues.

BTW, I meant to say the house has a hip roof all around. I shouldn't confuse that with "shed roof" but I do, verbally anyway.

I read of an innovation some years ago that used shower water going down the drain to save energy. It's probably only practical if the water heater is near the shower, and I would think it would work well with flash heaters. They had the outside of the drain pipe circle by thin copper line that the cold water entering the water heater would first pass through. They claimed that when draining the water runs down the sides of the pipe, unless the volume is so great, such as emptying the bath tub, that the drain line would be a solid stream of water. Supposedly transferred a decent amount of heat from waste water to new.

This only makes sense as water will wick to a surface. Not sure if this idea is highly useful but it does point to the thought that even while draining the 2nd floor sink, the upper part of the vent would still provide venting for the shower/tub below.

Next time I'm in the house alone, I'm going to fill the tub about 1/4 full, go up and fill the sink pretty full, then drain the tub and run up to drain the sink while the tub is still draining, just to observe the worst case scenario and see what happens. Doing it clandestine as I don't want them to wonder why I'm pulling this experiment.

She would just get neurotic and I'm equally certain she would ***** about the cost of moving the 1 and 1/2 ABS pipe 4 feet sideways. Not to mention, drilling holes that big, in addition to the unavoidable holes for supply lines, would weaken the studs (non bearing wall) such that the integrity of hanging the wall mount vanity (dumb design, IMO -- cutesy) from those studs might be compromised. And there's yet another vent line in the way anyhow, getting around that would be a real drag, if possible, that is.

This house is weird. All of the vent lines do a 90 degree turn in the attic and head over to the soffits. Not sure if that's even code. sewer gas could fill the attic. I told her she should have one big ridge vent put in that could handle both baths (next to each other) and have a vent opening included next to it -- cooler in summer.

I have often used loop vents for sinks with good results.

I didn't fully understand all your explanations about the attic and ridge venting. If there's not a vent going straight up for the plumbing that seems like trouble to me.....maybe not in sunny california, but illegal here I believe.

It looked a bit fishy to me. First and only time I've seen it.

Any results?

I'm curious as to the results of this experiment.

X2. Seems like it would be easier to run them straight up thru the roof.

Haven't had the chance yet. I'll probably be over there in a couple of weeks. I wanted to do it w/o attracting too much notice as I don't want them to think there's a problem, and I really doubt there is going to be one around this.

The roof is this artsy trendy blue lacquered terra cotta tiles stuff. Much easier to push a roof jack up through composition or cedar shingles than this stuff. There is one roof vent going through on the other side of the house but aside from that, the roof is virgin tile.

Is there any way to "marry" the 1-1/2" with the one roof vent you already have, or is that too far away and that much more of a problem?

2ndly, I'm willing to bet she didn't get all the permits needed, did she, eh?

That's probably why she's hesitant about poking holes in the roof...might lead one to think something, construction-wise/code-wise, is going on inside?

Eh? ;)

What, me work without permits? Never, I tell you!!

The one that does poke through the roof is on the other side of house beyond a cathedral ceiling -- the living room, gynormous. The roof is very busy on this house. A bunch of stuff going on, bits of the house go this way and that. Cutesy trendy.

The main reason she didn't want to go through the roof was expense. She just bought it and she says her cash flow is tapped out bigtime.

I advised her that she should get a ridge vent, not the entire ridge, just in one spot, for the attic portion above the bedrooms (separated from the other attic areas by the cathedral ceiling) as it has none -- heat build up, etc., plus we could vent the other stuff up through it all in one spot. Should cut way down on cost and not look as bad as 4 or 5 pipes sticking up.

She says she'll probably go for it -- a roofing company gave me the name of a 100 lb. Vietnamese guy who's supposed to be a wizard with this stuff, and his light weight can't hurt.

My biggest concern would be improperly welded pipe.
I've seen that before in houses where the homeowner was doing interior work, and even out of some regular plumbers. They figure that vent isn't going to actually have water draining in it, so they do a shoddy job putting the vent line together. One house, the vent lines were just stuck together, not glued at all.
As for the tub draining, you should not have an issue, as tub drains allow air in from the overflow.

Hey good point, I hadn't thought of that.

I looked at what I could see of the line up in the attic. Looked like it was put together OK.