We purchased a house that is 105 years old about 4 years ago. Before we purchased the house the electrical and plumbing was upgraded. The plumb is all PVC. We have been remodeling since we purchase the house. I am now looking to remodeling the guest bathroom and need to move a toilet about 6 feet. The house in on a Pier and Beam foundation and has about 3’ access under the guest bathroom. I recently went under the house to look at the plumbing and evaluate the project. I found the following:

There is a 3" main sewer line running directly to the septic system. Right before the 3" line exits the house there is a Y and another 3" line goes off to the master bathroom. The 3" line that I am going to be working on is to the guest bedroom and is about 20' long and supports drainage for a toilet, kitchen sink, and washing machine. The toilet drains into the 3" line at the end (furthest from the septic system) and the 1.5” kitchen sink drain and 1.5” washing machine drain T into the 3” line about 12” downstream of the toilet. The only vent I can find is the wet vent back to the kitchen sink stack. I’m not too impressed with the venting.

The only thing I can think to do is to basically cut about a 6’ section out of the 3” sewer pipe and reproduce what I have now by lengthening the kitchen sink drain and washing machine drain and tying then in downstream of the toilet. By shorting the 3” pipe it would basically reproduce what I have now. Venting seems to be a problem, but as I said it has been working for the last 4 years.
Does anyone have a better solution?

Now if you could just draw what you said we probably could picture it better

A diagram of the sewer is attached.

Hi old house...


Lots of issues with the plumbing for sure. However, I don't think we need to go into too much on it as you are changing the plumbing around anyway... ;) It is interesting to note that there are two things that should never be connected to a toilet drain as a WET VENT... YUP! A kitchen sink and washing machine... :) Unbelievable... huh? Also note here that tee fittings are not allowed in horizontal drain lines... so be sure to use wye fittings here.

Anyway, to install the new toilet I would have you begin by cutting out the old toilet elbow and then install an 3" end clean out in its place (see image).

Then you will want to cut a 3" wye into the main drain line about 4-6 feet away from where the new toilet will be located. Install a 3" test tee for a cleanout and then install a 3" street 45 into the test tee to square it up if needed. Then install a 3"x2" wye, rolled above the center of the toilet drain pipe for a new vent (we will discuss this more in a minute). End the run of 3" using a 3" elbow directly into the new toilet flange.

If the lavatory (sink) in the bathroom is vented then I would have you run the 2" vent from the toilet and connect it onto the sink drain. Here, the lavtory drain/vent can act as a legal WET VENT for the toilet. If no sink vent then you will need to decide if you want to run the 2" vent up and out the roof... I would... ;)

Check out the image below... let me know if you have questions.

MARK

Thanks for the information and the diagram. It is very helpful and is increasing my badly needed skills as a Do It Yourself plumber.

On the diagram where would you tie in the washing machine?

Thanks in advance for your help.

I left the washing machine and sink where it was... trying not to make a big deal of this for you. As you said, "it has been working for the last 4 years".

If you want to repipe all this correctly using proper vents and fittings for the washing machine and kitchen sink let me know and I'll draw it up over the next couple days.

MARK

Sorry to be a little dense or didn’t explain properly, but on the modified diagram it shows a sink wet venting the toilet. I assumed that was the kitchen sink that I showed on the original diagram. I did not include the bathroom sink on the diagram because that sink is drained in to a gray water system that is separate from the septic system.

As far as I can see looking on the roof and under the house the only vent stack close to the bathroom is the Kitchen sink. The sink in the bathroom is drained in to a gray water system and does not drain to the septic system. I have updated my diagram to help understand my situation.

Any help would be appreciated.

Hi oldhouse...

I see the problem. I called the sink a LAVATORY and in my area that is a BATHROOM sink... ;)

With the updated info. Given, I would stick with my first drawing only run the 2" pipe up and out the roof as a separate vent for the toilet. This will at the least give you another properly vented fixture.

Otherwise, when you open that wall you showed in your diagram, let me know what you find for venting. If there is a 2" vent in that wall, you can probably connect the 2" toilet vent into that vent at a minimum of 42" off the finish floor. Should be nbo issue connecting vents between the septic system and the gray water system.

MARK

I found a 2" vent in the wall directly across the room from where I am moving the toilet. This vent goes directly through the roof and down to the gray water main drain. My only access to the vent is under the floor in the crawl space. This vent looks totally dry but I will know more when I open the wall. The vent is about 8 feet (line of sight) from where the new toilet will be. I believe I can a run a vent line from that in the crawl space to the top of the toilet drain line with an acceptable slope. Can I vent the toilet using this vent? Is this acceptable? There is an attic room that covers about one half this bathroom and the attic room is directly over where I would like to move the toilet. This attic room makes it impossible to access the roof and vent the toilet.

I'm confident that you can connect into this 2" vent, but you must connect into it at least 42" off the floor, or run the toilet vent up to a point in the ceiling where you can connect into the existing vent up there...

Back to you...

I checked with the previous owner of the house and he is not sure how or if there are vent in the bathroom. What I am sure of is there is a vent in the wall opposite where the new toilet is going to be. I've attached a drawing which I hope will solve all the venting problems.

Any feed back would be greatly appreciated.

Thanks in advance.

Lonny

Hi Lonny...


Are those orange dots in your new diagram showing me that you are connecting vents into the drain lines, connecting all of them together and then running the 2" up and connecting into the existing vent? It isn't how vents work...

There are just so many rules....

Vents must roll above the center line of the drain they serve IF the drain line/PTRAP is at or below the floor. If the drain line/PTRAP is above the floor, such as washing machines, sinks, etc. then the vent must come off above the PTRAP.

Vents cannot connect together as you show... ALL the vents need to run above the floor to 42" before any of them connect into a main vent. In other words, all vents in a bathroom battery or on a single floor must connect at least 6" higher than the flood level rim of the highest fixture... in most cases the bathroom sink, the kitchen sink or the washing machine.

Say a drain clogs and you have a vent connected improperly. Here, the vent could act as the drain line and you would never know the drain was clogged. This has greater potential for major issues as the number of units in a building multiply.

Messy huh..

There may be another solution or two here. Let me think on it a bit. Please respond to this post and let me know your thoughts...O.K.??

MARK

.

:rolleyes::rolleyes:Mark,

I'm 62 years old and working on this house is keeping me a little younger, but sometime I get a little dense. I've attached another diagram trying to follow your lead. The orange dots are connections. It is impossible to take the vents overhead, there is no access because of an attic room directly above the bathroom. What I have done in the diagram is to take the vents from the roof vent in the wall, down through the crawl space, and back up in the walls behind the appliances to the 42" height. Let me know if I'm getting closer.

Thanks for your help.

Lonny

Mark,

If I'm on the right track I left a couple of things off. New version of the Diagram attached.

Thanks in advance for your help]

Hi Lonny...

Don't shoot the messenger here... OK... :rolleyes:

The way you are piping vents is simply not close to how vents work. You cannot run vents up and down the way you are proposing.

I think you would be best to run a new 2" toilet vent and connect it into the existing 2" vent in the wall by the shower. Connect the toilet vent into the existing vent at 42" minimum off the finish floor (see 1st image below). That finishes the toilet.

After that, if you want to add some vents to your system... you may be able to install AAVS (air admitance valves) and PTRAPS. These "mechanical vents" are not legal in most states, but they are sold and used everywhere. Here, the vents are installed at a minimum of 4"-6" (can be higher) above the PTRAPS they will serve. The AAVS must be accessible at all times, or at the least have an access panel that allows easy access to replace them in case one should fail down the road someday... see images.

The picture of the threaded black plastic unit is one kind of AAV. They sell different kinds as can be seen on the other pictures. The red line pictures of horizontal VS vertical apply to a washing machine and using a ptrap and AAV. The last two pictures show a bathroom or kitchen sink using a ptrap and an AAV.

These mechanical vents will be a much better alternative to running all the up and down vent pipes you proposed... eliminates all that piping.

Otherwise, you will need to open the ceiling and run new vents into the existing vent... no way around that other than the AAVS.

Back to you...

MARK

.

Mark,

Thanks for your response. I'm disappointed and seem no closer to a solution.

I've look at AAVs. The sink is a pedestal sink and I am not sure how to make an AAV work. Can you put an AAV in the crawl space? That is the only place on the shower I think you could place it.

I'm an old math major and I must admit that I don't understand the physics of the up and down vents. The water pull negative pressure on the vent and pulls air from the roof vent. I can't understand how the up and down makes a difference. I could run a separate line for each appliance to the roof vent in the wall at the 42" height but I still have to route down through the crawl space. I would like to run a vent from the existing roof vent around the room at the 42" level, but because I am not sure how to make 90 degree turns in existing walls with some being stress bearing, I'm looking for alternatives. Can you explain the physics of up and down? If we can make AAVs work I am all for it. Any suggestion for the pedestal sink and shower?

Back to you.

Lonny

Hey Lonny...

I understand the frustration. We spend years in school learning how drains and vents work together in the best way to keep sewer gasses from getting into people's homes... so don't be too hard on yourself... seems to me you're doin' fine!

Here is a couple pictures of how some bathrooms/fixtures get piped properly. Ignore most of the info... doesn't apply to you with the two different waste systems. Focus on how the vents connect together... some come above the drainline, some come above the PTRAPS... all connect above the floor at 42" minimum before a main vent goes into an attic or out the roof.

Code requires that rain water that enters the vent through the roof vent drain by gravity to the drain line... no UPS or DOWNS about it. After a vent reaches the level of the drain pipe... it CANNOT become a vent pipe again... it's a drain pipe.

Let me know if that helped.

Finally, I think you should put an AAV and PTRAP on the washing machine (above floor) and the kitchen sink (under cabinet) because it is so easy to do.

If you have a pedastal sink...I'd leave that alone. Including the new AAVS and the new 2" vent for the toilet piped correctly and seems to me you are leaps and bouds ahead here... ;)

MARK

Hey Mark,

Thanks again for your valuable feedback. I must admit with your help I've learned a lot. In your last few answers you gave me a couple of rules; the vent must gravity feed rain water enter the roof vent to the drain and that in the event of a clogged drain the backup water must not enter the venting system. It seems to me that my last drawing met those rules. I have no wet vents in the bathroom, all vent line below the floor slope towards the roof vent and the vents loop 42” above the floor restricting any backup enter the vent system. Therefore I must not be interpreting my drawing correctly or there must be another rule I don’t know about. If you could fill in that blanks I would be greatly appreciate it.

I have included a drawing from Stanley Complete Plumbing show an Island Sink that is vented with a loop vent that enters the venting system below the floor. This seems to me as an up and down vent. What keeps me from using the same venting technique for the sink and shower and running a direct vent from the roof vent to the toilet as you have shown previously? I’ve included yet another drawing and a picture of the Island Sink loop vent.

As always, your feedback is greatly appreciated.

Lonny

Hi Lonny...

Nice try there... really... :) However, the island sink vent that you posted is only to be used under special circumstances and is altogether simply too much work. Why not just use the AAVs as I mentioned?

In terms of understanding venting as I presented... again, there is a reason we go to school for YEARS... venting is not something learned in a few posts. The pictures of the venting systems I posted look nothing like your drawings for a reason... they are properly piped/pitched and vented fixtures. You keep telling me you can't do what I tell you needs to be done... fact is you can... you just don't want to open up the walls and ceilings... right? In plumbing, as much as we have too, when required we open up walls and ceilings.

As much as I would like to tell you to do whatever you want, I can't... I am a plumber and I am telling you that vents need to connect as they are drawn in all my drawings. If you can't or won't pipe as required then you either go with the vented toilet and the AAVS or you start to make things up and use island vents for everything... I guess... ;)

I wish I could give you an easier answer, but can't. Plumbing is an engineered discipline... no shortcuts.

I am glad to discuss this with you as much as you want... back to you.

MARK

Hi Mark,

Thanks for the feedback. As you can tell, I can be a bit hardheaded. I would like to follow your suggestion and us AAVs, but I don’t see how to use an AAV on the shower when the P-Trap is below the floor level. If you install an AAV in the crawl space there are a lot of creep crawly thing that could cause problems. If you install it in the wall you have no access. If you have a venting suggestion for the shower, I would feel confident we have a good venting solution.

My father a very long time ago gave me some very good advice that has served me well. He said when you have a problem, you want a problem that you can through money at and solve, because the alternative is really bad. Unless we can find a venting solution for the shower, I think I’m going to have to through money at it. Therefore I’m looking at building a soffit one foot deep and 2 foot wide around 3 walls of the bathroom. In the soffit I can tie in to the existing roof vent and wrap a vent around to each appliance. The bathroom has a 10 foot ceiling and I would have to tie in to the roof vent at that level. I’ve included yet another diagram.

Let me know if you can think of how to vent the shower. If you can’t think of anything, let me know if the soffit solution will work.

Lonny

Mark,

Somehow I thought you needed one AAV per appliance. Today after sending you the last answer, I began studying AAVs and found that is not true. I’ve tried to copy a solution I found in an AAV manufacturer brochure and using that information redid a diagram using one AAV. As you stated it is an easy straight forward solution. Please take a look. It is a lot easier and less costly than building soffits.

Thanks in advance.

Lonny

If you run the toilet vent and connect that into the existing vent and then run the washing machine vent into the existing vent then you are really in good shape here. The shower should also be able to bevented in the same manner... just take the vent off the top and run that in with all the other vents above the floor.

The individual vent for the kitchen sink is great, but remember the AAV will work real nice under the sink here so may not be necessary to run that vent up and out the roof... although it would, of course, be the best job!

The AAV for the pedestal is good!

MARK

I'm not sure I understood what you said. I think you said the Washing Machine and Toilet was okay. You lost me on the shower. Can the shower and the sink be vented by the AAV as I showed in my drawing?

Hi Lonny:

Venting the shower using the AAV off the pedestal sink is an improvement to an unvented shower STRAP, for sure, but the shower would still be considered unvented. Here, if an STRAP remains, it is an unvented fixture... vent must come above the PTRAP.

You would need to add an AAV in the crawlspace (so it is 6 inches above the trap (up in the joist bay) OR pipe it up as I show in red in the drawing below... see image.

Let me know if that is more clear...

MARK

Mark,

I am continuing to make progress on the bathroom. The new "level" subfloor is in, new recessed lights are installed, and the remaining electrical has been stubbed out. Executing our plumbing plan is underway. However, I have an issue with the plumbing of the pedestal sink. Because the plumbing will be visible on a pedestal sink we are using brushed nickel supply, drain lines, and stops. This makes installing an AAV between the P-Trap and wall a problem due to both the way it looks and the amount of room between the wall and the sink drain center (8 ½”). Is it acceptable to place the AAV below the floor in the crawl space? I’ve included a diagram showing our original plan and hopefully an alternative.

Suggestions would be greatly appreciated.

Thanks,

Lonny

Hey Lonny

The AAV is supposed to go at least 4" above the Ptrap...simply not legal plumbing today if done any other way...*OUCH*! Best result would come from installing the AAV inside the wall with an access panel for the future (could even be just behind the mirror).

However, that being stated to free me up of any guilt...:cool:...you could pipe the 1.5" PVC ptrap and the AAV in the crawlspace with the trap at about 6 inches below the floor... the AAV would come out of the ptrap and run up close to the floor boards. Then you can run a straight shot of 1.25" tubular drain pipe from the sink drain assembly (plastic or metal as it won't be seen inside the pedestal base) through the floor and connect into the 1.5" PVC using an 1.5" PVC x 1.25" trap adapter at the PTRAP.

I don't like this option but it was used for a long time way back when and it was better than no vent at all!

Back to you...

MARK

PS: Check to be sure that you have a straight shot from the sink drain down through the pedestal base. If you don't you may need to use a diamond saw to cut some of the bottom of the base...let me know.

Mark,

Thanks for getting back to me. I cannot take the drain through the pedestal due to the pedestal mounting bolt directly below the sink drain. Putting the AAV behind the mirror is a good option. There are electrical wires in that location, but that should not be a big problem. Because the mirror is oval and side mounts, so that it can be tilted, it is about 1 1/2" away from the wall. I now need to convince my wife that you will not be able to see the AAV access panel.

After a lot of thought regarding the subfloor I decided not to use a self leveling compound to level the floor. The house's pier and beams are on clay and there is a small amount of movement between wet winter and dry summers and I was concerned that the self leveling compound would breakup over time. Therefore I laid down a 15# felt vapor barrier on the tong and grove subfloor, then roofing shingles to get a good level, then ¾” T & G plywood screwed down on a 6” grid. The floor is now level with no movement. I hope this solution will hold up over time.

I better get back to work. Thanks for your help.

Lonny

Hi Lonny:

The vent behind the mirror is definitely the best choice!

In terms of the floor, I think you should be fine. I've done the same many times over the years... ;)

Keep me posted.

MARK

Hi Mark,

I am now working under the house connecting all the plumbing. I have a short distance, about 3 feet or less from the toilet to the horizontal (with at least a ¼” drop per foot) main drain. Is it acceptable to run the closet bend horizontal with no drop for about 3 feet? The distance is so short I am having a problem finding any fitting that doesn’t drop too fast to match the main sewer drain. I’ve attach a drawing, but it is difficult to draw in 3 dimensions.

Thanks again for your help

Post Edit

I've edited this post and added an alternative that gives me rotation in 3 axises. Let me know what you think. Thanks

Post Edit 2

Simplified the Sewer Connection Diagram by elimating the Long 90 and the Wye and replaced them with a Combination Y- 1/8. Again let me know what you think.

Lonny

Hi Lonny... see my thoughts on this in RED below... ;)

MARK