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Small Cabin Forum / Cabin Construction / Plumbing help needed
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Tarmetto
Member
# Posted: 1 Oct 2015 07:54 - Edited by: Tarmetto
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Other than basic repairs, I have no plumbing experience, but there's not much that I can't do with a little education.
We have had 3 plumbers come out and look at our new bath house for an estimate. So far...we haven't heard back from any of them (frustrating!). I don't understand that...but it is what it is.
So, I'm going with the most reliable person...ME!

Now, I know that I can plumb it, and that it will work, but I have no idea how to do it so that it will pass inspection. This is in SC, and the inspectors are fairly forgiving for DIY guys, and I have permits in hand. Water supply lines aren't a problem...draining and venting is where I need help.

I wonder if someone here, who knows, could advise me based on the attached sketch.



bldginsp
Member
# Posted: 1 Oct 2015 08:38 - Edited by: bldginsp
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The reason you haven't heard from the plumbers is because they want you to call them. The person that calls is in a lesser bargaining position. If you can afford to pay them, it will happen faster with fewer if any mistakes. But you can do it yourself, just be ready to cut your work to pieces to fix it if the inspector finds a mistake.

So I take it that you are doing underfloor plumbing in a crawl space.
-Toilet minimum pipe diameter 3", vent 2"
-Shower min pipe 2", vent 1-1/2"
-Sink drain and vent 1-1/2.
-Laundry drain 2", 1-1/2" vent.

Vents must always come up off the drain downstream of where the waste enters the line after the trap, and must always come off the waste line above its center so waste cannot backflow into the vent.

The toilet is a trap and requires no trap under the floor. The shower must have a 2" trap under the floor. Locate the washer trap about 12" off the floor, and make the pipe leading to it no more than 30".

Waste lines must flow downhill at 1/4" per foot. Make as few turns as possible. Include an end of line cleanout outside the wall opposite the direction of flow so you can get a snake in the line to clean it. Code says a cleanout every 135 degrees of bend.

Secure all piping to the wall. Ream all copper cut ends.

Never use a sanitary T to introduce flow to a horizontal section. Sanitary Ts are only for leading horizontal flow to vertical flow.

All horizontal changes in direction should be done with long sweeps.

Never stress ABS. If you force it into location you are stressing the joints and they will eventually break if the stress is enough. Its cheap stuff but works fine if not stressed.

Never make an 'S' trap. If you don't know what that is look it up. Kind of hard to describe. Basically, vent before a downward turn.

Never decrease pipe size in direction of flow. When joining vents never reduce pipe size. Join vents in the wall and attic into a single 3" vent to penetrate the roof, or if necessary, use multiple penetrations. Total size of venting should equal size of final waste line. The one exception to the 'no decrease' rule is toilets- a 4" toilet can reduce to 3", but only at the toilet with a special fitting which is commonly used.

Inspector will want to see the whole system under water test to check for leaks. Cap off at the lowest point, plug all ends, and fill with water to the top of the vents.

Usually it's done in two inspections, first the underfloor plumbing before you lay the plywood, then the venting is checked at rough frame after the roof is up. But you can do it all at once so long as it is exposed. First rule of inspections- get it inspected before you cover it up. For the underfloor inspection have one 10' length of pipe sticking up in the air for the water test, fill to the top of that pipe.

Cant think of any thing more right now, except the three main rules of plumbing:

1-**** flows downhill
2-Eat your lunch with a fork
3-Payday is on Friday.

Tarmetto
Member
# Posted: 1 Oct 2015 09:18
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Thanks bldginsp!

Can I run drain lines from the outdoor kitchen sink, the washer, and the shower, into one main line (3" maybe)?
Is there any reason why I couldn't use 2 4" san/tees (one pointed towards the toilet (fed by toilet and bath sink), and one pointed towards the outside sink (fed by shower/washer/outside sink) installed vertically at the sewer stub? (building is on pilings...open-air crawl space...LOL)

toyota_mdt_tech
Member
# Posted: 1 Oct 2015 11:38
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bldginsp, nice post, full of great info too.

Another one of the many assets of this forum.

And to Tarmetto, for supply lines, use the red and blue pex, get the crimper tool that looks like bolt cutters. Makes plumbing a snap. And survives freezing well too. You cant pour concrete over it unless its in a sleeve if memory serves me correct.

bldginsp
Member
# Posted: 1 Oct 2015 15:15
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Thanks Toyota. I guess years of looking at other people's work has paid off. But when I went to do my own plumbing, I did a lot of head scratching. Good plumbers are artists in their own right.

Yes Tarmetto you can use santees as you describe. They make a double santee which might work for what you describe. Don't be afraid to move the sewer stub itself if you need to and are able. All the fixtures you are connecting to the system can drain to a single 3" line, I don't think you are anywhere near the limit for 3"

I personally don't like Pex because they put a lot of chemicals in it to make it handle hot water. But that's a personal choice of mine. Some people say that copper is bad for because it is a heavy metal. PVC is definitely the worst, though.

adakseabee
Member
# Posted: 3 Oct 2015 21:45
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I would swap the positions of the washer and dryer. That way you could have your washer hot and cold supply lines and drain on an interior wall along with the supply lines to your shower. If you have the room, make the wall between the shower and washer (assuming you swap its location with the dryer) with 2x6s to give you more room for the plumbing.

Ensure that you protect your plumbing in the walls from inadvertent penetration by nails and screws used to attach wallboard over the 2x4s and/or 2x6s.

toyota_mdt_tech
Member
# Posted: 4 Oct 2015 20:05
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Quoting: adakseabee
I would swap the positions of the washer and dryer.



He should anyway, the dryer always goes to the right of the washer. Ever notice what way the dryer door opens, its made to easily transfer clothes from washer to the dryer.

Good catch adakseabee

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