Discussion in 'Plumbing Forum, Professional & DIY Advice' started by kmuddzy, Dec 15, 2011.

1. ### kmuddzyMember

Joined:
Nov 30, 2011
Location:
New Jersey
Here is a nice link to Bert Polk's plumbing tips

I am a DYI’er and I’m excited to do my first house plumbing rough-in for a house remodel and new addition. I tried to answer as many questions as I could by researching the web but I need to get a few answers I couldn’t find as well as confirm some answers I found. I apologize for the number of questions but I didn’t want to post 10 different threads. I would pay a qualified plumber an hourly rate to check in on me while I'm doing this but I haven't found that person, either. Thanks in advance for your help!!!

First, horizontal or horizontally means that there is at least a Â¼” slope.

1. Can I run a 1 Â½” vanity drain horizontal along a 2x4 wall and around a 90deg corner? i.e. can I use a 90deg fitting to turn the corner?

2. After the shower’s p-trap, I am showing a 2” drain running to a ‘T’ and the top of the ‘T’ is a 1.5” vent. Can a 1.5” vanity drain ‘T’ to this 1.5” vent pipe for drainage purposes (creating about a 4’ section of vertical wet vent for the shower)? If I do this should the “wet vent” section be 2 inches?

3. How far can a vanity 1 Â½” sink drain run horizontal along a wall before it turns down to run to 3” sewer pipe?

4. I have a 3” toilet drain that runs 5’ horizontally to a “T”. Can the top of the “T” be 1.5” for the vent?

5. What is the largest diameter pipe that can go through double 2x6” top plate on a structural wall?

6. Am I correct that the minimum slope on a 2 inch or less pipe is Â¼” per ft, 3” or larger is 1/8” per ft and on all pipe the maximum slope is Â½” per ft ?

7. Am I correct that if a horizontal run has to be greater than Â½” per foot then a 45 degree drop should be used and there is no minimum or maximum length to this 45 degree drop before it returns to the horizontal pipe slope?

8. If I have a 1 Â½” kitchen sink vent pipe extending vertically to the 2nd floor and then running horizontal for 20’ before going vertical through the attic to the roof. During the 20’ horizontal length I will have the 1 Â½” vents for a washer, 2 vanities, a shower and a tub connecting to it. Should this vent pipe be increased to 2” somewhere along the way or can 1 Â½” run to the roof?

9. Am I correct that all drain pipes are a min. 1.5” except for a shower (2”) and a toilet (3”)?

10. What’s the minimum size joist one can use below a shower if the p-trap is as tight to the drain as it can be? I.e. will a 2” shower p-trap fit within the 7” of a 2x8 joist bay below it (old house joists)?

11. If I’m correct, one can drill a hole in a joist as long as the diameter is no more than 1/4 the height and the hole is not located in the middle 1/3rd of the length. Therefore I cannot drill a 2” hole in my 2x8 joists. BUT, am I allowed to cut the joist entirely, install a double 2x8 header to the 2 adjacent joists (joists will NOT be sistered)?

12. Is there a min and maximum distance from a Tub or shower drain to the p-trap below it? I have 2x12 floor I-joists and then some space below those where I would like to locate the p-trap before the drains run horizontal.

13. Can a 3” Radon pipe travel horizontally (90deg bend) for 5’ before going vertical again (another 90deg bend)?

14. Does the top elevation of a 3” radon pipe have to be within a certain distance from the elevation of the peak of the roof? My 1 radon pipe can exit straight up to the roof but it will exit within 2’ of the gutters. The only option I have is to run it up along the rafters and then exit the roof higher up.

15. The existing house had a kitchen, 1 full bath and laundry – all draining down to a 3” PVC pipe running to the septic. Now we are adding 2 full bathrooms. Will the 3” PVC pipe be adequate?

I hope the above is clear. Thanks for your help!!!!
Keith

Here is a nice link to Bert Polk's plumbing tips

Last edited by a moderator: Dec 15, 2011

Joined:
Aug 17, 2004
Occupation:
Plumber
Location:
Bothell, Washington
1. Can I run a 1 Â½” vanity drain horizontal along a 2x4 wall and around a 90deg corner? i.e. can I use a 90deg fitting to turn the corner?

You can have 135 degree of change of direction per cleanout.

2. After the shower’s p-trap, I am showing a 2” drain running to a ‘T’ and the top of the ‘T’ is a 1.5” vent. Can a 1.5” vanity drain ‘T’ to this 1.5” vent pipe for drainage purposes (creating about a 4’ section of vertical wet vent for the shower)? If I do this should the “wet vent” section be 2 inches?

A wet vent needs to be two pipe sizes larger and a minimum of 2". Since a lav can use 1-1/4", 2" would work, as long as you are on the same floor.

3. How far can a vanity 1 Â½” sink drain run horizontal along a wall before it turns down to run to 3” sewer pipe?

As far as you like.
These are UPC trap arm lengths for the venting.
1.5" trap arm length, 42"
2.0" trap arm length, 60"
3.0" trap arm length, 72"
4.0" trap arm length, 10 feet unless it's for a toilet, then six feet.

4. I have a 3” toilet drain that runs 5’ horizontally to a “T”. Can the top of the “T” be 1.5” for the vent?

In many codes you would need at least a 2" vent.

5. What is the largest diameter pipe that can go through double 2x6” top plate on a structural wall?

You can cut the entire plate out, both top and bottom in most cases. It depends on the bearing of the structure. We would need structural plans and pictures to say more.

6. Am I correct that the minimum slope on a 2 inch or less pipe is Â¼” per ft, 3” or larger is 1/8” per ft and on all pipe the maximum slope is Â½” per ft ?

Minimum slope is 1/4" per foot unless you are running 4" and you have permission from the plumbing inspector.

8. If I have a 1 Â½” kitchen sink vent pipe extending vertically to the 2nd floor and then running horizontal for 20’ before going vertical through the attic to the roof. During the 20’ horizontal length I will have the 1 Â½” vents for a washer, 2 vanities, a shower and a tub connecting to it. Should this vent pipe be increased to 2” somewhere along the way or can 1 Â½” run to the roof?

You need to count the units up as you go and work backwards.
If a vent's horizontal is more then 1/3 the distance of the vertical, then you will need to go up one size.

9. Am I correct that all drain pipes are a min. 1.5” except for a shower (2”) and a toilet (3”)?

No. Most sinks, including kitchen and laundry need 2". A lav can use 1-1/4".
Tubs require 2" as do showers.
If you have four toilets, then where the 4th toilet enters, you need to bump it to 4".
Outside the foundation, the sewer will be run in 4" regardless.
Your code book will list all of the minimum sizes for each fixture.

10. What’s the minimum size joist one can use below a shower if the p-trap is as tight to the drain as it can be? I.e. will a 2” shower p-trap fit within the 7” of a 2x8 joist bay below it (old house joists)?

It depends on how high the pipe is located. If you have to drill through the joist, then a 2x8 won't fit it. If you are running with the joist, then it should fit. The pipe would need to be run high.

12. Is there a min and maximum distance from a Tub or shower drain to the p-trap below it? I have 2x12 floor I-joists and then some space below those where I would like to locate the p-trap before the drains run horizontal.

We install the p-traps directly below the waste and overflow drains.

15. The existing house had a kitchen, 1 full bath and laundry – all draining down to a 3” PVC pipe running to the septic. Now we are adding 2 full bathrooms. Will the 3” PVC pipe be adequate?

3" will handle up to three toilets. When a fourth bathroom is installed, that's when you would need 4".

Last edited: Dec 16, 2011

4. ### kmuddzyMember

Joined:
Nov 30, 2011
Location:
New Jersey
Wow - great stuff Terry and thank you so much for your quick reply. I will digest this - I can see I need to change a few things but most look feasible. I will check with the inspector on the radon and joist header questions. Thanks again! Keith

Oh - & thanks for Bert's plumbing tips -I wish I would've found those first!!!!

Last edited: Dec 15, 2011
5. ### bluebinkyMember

Joined:
Aug 31, 2011
Occupation:
Software Engineer
Location:
Santa Clara, CA
Terry is , of course, a far better expert than I am.

To add a little clarification, someone correct me if I'm wrong...

The horizontal 90 for the vanity drain will have to be a long-sweep, not a tiny short-turn vent fitting. The part about running the horizontal drain as far as you like assumes that there is a vent at the vanity.

6. ### hjModerator & Master PlumberStaff Member

Joined:
Aug 31, 2004
Occupation:
Plumber
Location:
Cave Creek, Arizona
qquote; 3. How far can a vanity 1 Â½” sink drain run horizontal along a wall before it turns down to run to 3” sewer pipe?

As far as you like.

In my opinion "as far as you like" would be limited to about 3 or 4 feet. In EVERTHING Terry answered, it should always be remembered, that what he said, and HOW YOU INTERPRET IT, can be vastly different when you actually install the piping. You have taken on a VERY ambitious project as a "beginning plumber". IF plumbing could be learned by reading a couple of books and asking questions over the Internet, we would not hav to go to school for 3 years and serve a 5 year apprenticeship. The problem with "hiring" a plumber to supervise you is, as I have found out numerous times, WHAT he tells you to do and what you actually do may not be the same, and then arguments occur over who said what, and then the customer does NOT want to redo whatever is wrong and blames the plumber for the error. In other words, no matter how much you pay him, it is seldom worth the headache and frustration.

7. ### kmuddzyMember

Joined:
Nov 30, 2011
Location:
New Jersey
Thanks. I haven't bought the supplies yet. If it is a long sweep 90deg elbow do they fit inside a 90deg corner of a 2x4 wall (non-structural) or will some be exposed on the inside corner of the wall?

Thanks for your input and very good points. I understand this is an ambitious project for my first rough-in. I would prefer to hire a plumber to do this but I'm building this addition for my wife's sister's family and they simply don't have \$10,000 in the budget to hire a plumber. I'm going to do the best I can and with the inspection/research/guidance and I believe I will end up with an acceptable plumbing job. I also understand the difficulties in hiring a plumber to oversee what I'm doing, which is why I haven't found the right person willing to do this. Either way, this will be an adventure and one that will take me a lot longer than an experienced plumber.

If you don't mind could you clarify your comment: " In my opinion "as far as you like" would be limited to about 3 or 4 feet."

I'm assuming that I can run a 1 1/2" bathroom vanity drain no more than 3' after the p-trap to a 1 1/2" "T" vent pipe and then after the vent I should be able to run the remaining 1 1/2" pipe horizontal for "as long as I want" before it tees into the shower's 2" wet drain/vent and heads down. Is this correct? Thanks again. Keith

Last edited: Dec 19, 2011

Joined:
Aug 17, 2004
Occupation:
Plumber
Location:
Bothell, Washington
You won't find any 1-1/4" PVC fittings that are legal for waste and vents. You will need to run that in 1-1/2"

You can also go up to 2" on the pipe after the vent is taken off. That hardly cost any more money, and it's much easier to keep clear after years of use. Also, if someone wants to add a second lav later, you will have the proper sizing for that.

9. ### kmuddzyMember

Joined:
Nov 30, 2011
Location:
New Jersey
OK - I can change that to 1 1/2" pipe. I was only looking at 1 1/4" since I need to make a 90 degree turn inside a 2x4 wall. I might be able to avoid the 90degree corner by running the 1 1/2" pipe down, under the floor and wye it to the shower drain. Is it Ok to tee a 1 1/2" or 2" vanity sink drain into a 2" shower drain (after the shower's p-trap but before the shower's vent 24" away)? Thanks, Keith

Joined:
Aug 17, 2004
Occupation:
Plumber
Location:
Bothell, Washington
Anything that comes in between a p-trap and vent makes the vent useless.

In most cases, you would vent everything that has a p-trap.

If you understand wet venting and it's rules, then a lav could be used to wet vent a shower. Assuming it's on the same floor and 2" pipe is being used. A few more things need to happen too.

Last edited: Dec 19, 2011
11. ### kmuddzyMember

Joined:
Nov 30, 2011
Location:
New Jersey
Thanks. I don't fully understand wet venting but I will look into it some more and see if it gives me a layout option that makes it easier for me.

12. ### jimboPlumber

Joined:
Aug 31, 2004
Location:
San Diego
"" [h=2]6. Am I correct that the minimum slope on a 2 inch or less pipe is Â¼” per ft, 3” or larger is 1/8” per ft and on all pipe the maximum slope is Â½” per ft ?
""

There is no maximum slope. Vertical is the maximum slope! Anyone who tries to tell you about the water outrunning the solids is perpetuating old wives tales.[/h]

13. ### Gary SwartIn the Trades

Joined:
Sep 1, 2004
Location:
Yakima WA
I gotta say I think you are starting down a long and expensive road tackling a job like this with zero plumbing knowledge. There are probably dozens of places you will screw up and have to redo the job to pass inspection. All of us DIY folks try jobs that are beyond our abilities at one time or another, and most of the time it costs us more than if we had admitted our shortcomings and hired the pro. I believe it was Clint Eastwood in "Dirty Harry" that quipped, "A man's got to know his limitations."

14. ### kmuddzyMember

Joined:
Nov 30, 2011
Location:
New Jersey
yes but if you don't have the money then there isn't much one can do about hiring a pro. My time is worth zero right now so if it takes me 10x longer then so be it. Besides, I've already done my own plumbing for my geothermal unit/hot water heater. It isn't near the magnitude of this job but I should be able to work through this knowing I will have to redo some things. Nobody knows their limitations until the try something and fail!

Last edited: Dec 19, 2011
15. ### bluebinkyMember

Joined:
Aug 31, 2011
Occupation:
Software Engineer
Location:
Santa Clara, CA
Yep, but that's not always a bad thing. If you just want to save money one time, then don't even try. Just hire a pro.

If you look at it as an investment in yourself or just want the personal satisfaction of accomplishment, then it might be worth spending more to do it yourself a few times.

Put another way, the hardest part about DIY is figuring out what you don't know ... something that seems to escape most people.

16. ### kmuddzyMember

Joined:
Nov 30, 2011
Location:
New Jersey
Here is my first ISOMETRIC schematic. The first image is a thumbnail showing the floor plan (brown lines) and the 2nd image is the enlarged bathroom plumbing. I never posted a pic here before so hopefully this will be legible.

Yellow = Drains
Lt. Blue = Vents
Green = Wet Vents
Red = bathroom fixtures
Brown = floor plan walls

A = 2" Shower/Vanity sink drain to basement
B = 2" Tub / Vanity sink drain to basement
C = 3" Toilet drain to basement

All vents are 2" except the two vanity sink vents which are 1 1/2" and the wet vents which are 2 1/2" (2 sizes larger than vanity drains). The vents all connect in the attic with a single 2" roof penetration. LEt me know your thoughts. THANKS and THANK YOU!

Last edited: Dec 19, 2011
17. ### hjModerator & Master PlumberStaff Member

Joined:
Aug 31, 2004
Occupation:
Plumber
Location:
Cave Creek, Arizona
If THAT system you drew costs \$10,000.00, you are talking to some VERY expensive plumbers. MOST new homes do not cost that much for their entire system. Is "acceptable" good enough for your sister? Acceptable could mean that it is just "marginal" as far as performance is concerned. If I were doing the installation, I think I would "simplify" it from your design.

Last edited by a moderator: Dec 20, 2011
18. ### kmuddzyMember

Joined:
Nov 30, 2011
Location:
New Jersey
That is only 1 bathroom. I got two quotes - \$10k and \$12.5k. These estimates includes the bathroom shown, the master bathroom, laundry, kitchen, water heater and propane stove/dryer. but you are right that I live in an expensive area - NJ sucks for that.

As far as acceptable goes or "simplifying" the design, I can't really comment on that. I'm doing the best I can and there isn't more that I can do. You make it sound like one should just create money or not do any work at all. I would never get anything done if things were that black and white.