Rerouting the bath drain

My bath drain, drains very slowly. It doesn't appear to be clogged with hair and it drains into a septic tank. No other drain seems to have a problem. However I was wondering if the way the previous owner routed the drain lines might be the source of the issue.
http://photos.imageevent.com/eigenvector/houseideas/websize/P9160042.JPG
Shows the drain. There are two obvious things that make me wonder. One, as you can see there is a wierd PVC joint right above the transition to the galvanized pipe - almost like they necked it down, you can see all the green joint compound. The other is the absolute horizontal pipe that runs from the tub drain to the PVC "T" junction. Could this be the source of my slow drain? I presume the vertical PVC pipe section is for the tub overflow drain - it doesn't go anywhere else and it isn't a vent so far as I can tell.
A couple of questions, if I were to snake the tub drain, would the trap cause problems Second, if I were to redesign the tub drain, how do I deal with the sewer? I presume that there is basically raw sewage all the way to the top of the tub drain "U" trap. Should I crack out the NBC suit and call in the EPA or are there alternatives to dealing with the sewer line?
BTW: I finally cleaned out the bulk of the spiders in that corner, as you can see its relatively clean now. The webs back there made the opening scenes of Raiders of the Lost Ark look like Martha Stewart dusting cobwebs.
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On Sat, 16 Sep 2006 17:56:37 -0700, "Eigenvector"

slow drain unless it's clogged with soap scum and hair, which is pretty common. You are correct that the vertical leg goes to the overflow.
You can try snaking the drain with a small diameter spring snake down through the overflow. If you use the type that you can spin you should be able get it through the trap. If the tub has a trip-lever stopper on the overflow plate, it will pull out up through the overflow when you remove the plate.
If you can't snake it or it doesn't help, you are going to have to take it apart. IIWM, I'd cut the galvanized leg midway between the trap and the stack, and replace the trap with a pvc one with a cleanout. You can couple the PVC to the galvanized with a fernco coupling.
You may find the galvanized piping is so corroded inside that it is restricting the flow. If that's the case, you are in for a bigger job.
Good luck,
Paul
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wrote:

cause a slow drain. You can snake thru the trap with any small snake.
Don Young
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wrote:

Uhhhgg, I was hoping you wouldn't say that. Well actually it won't be so bad, the pipe doesn't run very far before it dumps into the main septic line.
Just out of curiousity, is the galvanized and PVC line gonna be full of septic water?

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On Sat, 16 Sep 2006 21:07:07 -0700, "Eigenvector"
<snip>

a little old bath water in the bottom of the trap. (unless something is really, really wrong!)
Well, that's not quite true, it will probably have a pretty disgusting build-up of sludge, soap scum, hair, lint, etc. But no sewage or (ahem) waste. (Unless you have very unusual bath habits :-) )
Paul
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Eigenvector wrote:

Just curious, how do you know that?

I would say no, the section past the P trap seems to slope well but I can't see what happens after that.

Yes, should be the overlow

Shouldn't but it's always better to be very gentle when snaking old pipes.
Another think you may want to check is if that drain has a dedicated vent pipe http://en.wikipedia.org/wiki/Plumbing_drainage_venting and if that pipe is clogged. Birds, wasps, bees. etc have a passion for those vents.

Not sure what you mean here.

Actually no, that pipe should be empty when not draining water from the tub. Only the lower part of the trap should hold some grey water, but no sewage.

No, and no need to call the cavalry either. If you re-route the pipe (why?) or replace it, just stuck some rag on the septic side to keep the odor down until you'ready to reconnect. You don't want that rag to go all the way inside the pipe, right? No offense, but replacing that drainage pipe is a job is better left to a pro.

Now you have some very p...d off spiders there.
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Eigenvector wrote:

the tub drain "U" trap. Should I crack out the NBC suit and call in the EPA or are there alternatives to dealing with the sewer line?<<<<<
chill out......the "raw sewage" of which you are concerned is really just "grey water".....shower / bath drain water. The trap stays wet from use but the rest of the drain plumbing is empty .....everything just drains away....not supposed to have standing water anywhere except in the trap
Even "black water" is mostly water....esp after a few flushes of water only. Changing diapers is worse than either one..... :)
per the other replies, the trap & galv lines might be the problem. I'd Sawzall out everything from the new plastic tub /shower stuff to the iron T & replace it with new plastic parts. If the old metal parts are corroded & clogged...you fixed it!
If not, the problems further downstream (but I doubt it).
I had an upstairs shower back up into a downstairs sink (shared downstream line). I pulled the downstairs pedestal sink away from the way & snaked the common line from there......a week later no problems.
Usually a simple fix solves the problem.
cheers Bob
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