Proper venting for washer, sink, and water closet

[NurseJenny360]

Hello! For code reference, I'm living in Pierce County, WA. I have appreciated all of the advice/information I've read so far. I took the liberty of mirror-flipping the attached photo and adding the toilet with a vent to show my situation. Sorry for the long post.

We found significant carpenter ant damage and have been undergoing some renovations in this area. We moved our washer and dryer into the half bathroom to fix some issues where they were backing up at the previous location (placed there during a quick flip). In my photo, you can see that there is a 1.5" pipe coming up from the slab to the left of where the water closet goes. With the washer discharge hose hooked into the 1.5" drain, we have had no backing-up issues, but I know it isn't code to have a washer and sink drain to a single 1.5" pipe. My husband and I prefer not to hook the hose over a utility sink to drain.

This area was originally a garage/shop built between 1964 and 1967, converted to livable space in the 80s.

QUESTION:

If the window is moved, can the WC vent pipe be used if we tie in at 42" or above? I have seen conflicting information about this.

A new 2" drain would be placed similar to what is shown for both the washer and sink. This drain would tie into the WC drain after the vent and before the current clean out, buried just outside, further leading to the septic tank pump basin.

 

[wwhitney]

I'm not clear on what your question is, or what connectivity you have. Maybe draw and post a diagram of how the pipes are currently connected, and how you propose to connect them? But a few comments:

1) The WC requires a 2" vent. That could either be a dry vent (which can't be horizontal until 6" above the fixture flood rim, so such a dry vent needs to be taken off in the floor below a wall into which the vent can rise (minimum 45 degrees above level) immediately. Or it can be a wet vent, which in your case means that the lav would need to hit a 2x2x1.5" san-tee, so a 1.5" (or 1.25") lav trap arm going to a 2" lav drain with a 2" dry vent. Then that lav drain/wet vent would hit the 3" WC drain in a horizontal wye.

2) The lav needs its own dry vent. That could be a 1.5" dry vent if the lav is not being used to wet vent the WC, or a 2" dry vent if it is, as per point (1).

3) The washer standpipe needs its own dry vent, which can be 1.5", and its drainage may not join a wet vent. I.e. if you are using the lav to wet vent the WC, then the washer standpipe drain needs to join the lav and WC downstream of the wye where the lav joins the WC. [The portion of the lav drain considered a wet vent is from the lav san-tee (dry vent takeoff) to the wye where the lav joins the WC in a horizontal wye (which is the vent takeoff for the WC).]

4) Any dry vents may go horizontal or join other dry vents at a height of at least 6" above the fixture flood rims involved.

Cheers, Wayne

 

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[NurseJenny360]

If I understand what is going on with my current plumbing, I have a straight pipe in the slab that connects to the main septic drain pipe after the toilet vent. I dug out that area and took a picture for reference.

I'm not a great artist, but here is an attempt to draw what I am asking. Washer and lav would have their p-traps but would be wet-vented. Then, they would dry-vent to the current 2" vent for the toilet. The drain would connect to the septic drain outside similar to how it currently is but I would change it to a wye with a 2" instead of the current cast iron 1.5".

In my drawing, I think I made a mistake in that I would need to connect the washer and laundry vent before the horizontal portion connects to the vent stack. Correct?

I'm not 100% against adding a separate vent for the washer and lav because I will need to add one for a fan, but I was hoping to vent the fan through the soffit to avoid additional holes in the roof, or the top plate of the wall.

 

[wwhitney]

Let me try this approach: consider an elevation that is just above the flood rim of all the fixtures. At this elevation you will have 2 or 3 dry vents. Once you get 6" above this elevation, your dry vents may go horizontal and may combine with each other, so you only need to have one penetration through the roof if you prefer.

The option with 2 dry vents: you use the lav to wet vent the WC. A wet vent means a drain is simultaneously acting as a vent. So your lav trap arm goes to a 2x2x1-1/2 san-tee (located within 42" of the trap if you use a 1-1/2" trap), and the 2" top entry of the san-tee is the lav dry vent. The 2" exit is the lav drain/wet vent. The lav drain joins the WC drain in a 3x3x2 wye (or 3x2x3 wye) where both inlets are horizontal (2% slope). The washer drain joins downstream of this wye. The washer standpipe has a trap that is 6" to 18" above the finish floor, and it gets a a minimum 1-1/2" vent within 60" of the standpipe trap.

The option with 3 dry vents: each fixture gets its own dry vent. The dry vent has to come off the fixture drain, meaning the portion of the drain system hthat carries only that fixture. The requirements for the lav and washer dry vents are as previously, except the lav dry vent only has to be 1-1/2". The WC dry vent needs to be 2" and to come off the 3" WC fixture drain and rise vertically (at least 45 degrees above level), no horizontal portions below the floor. The length of the 3" pipe measured along the pipe (including vertical portions) from the closet flange to the dry vent take off has to be 72" or less.

Cheers, Wayne

 

[opplumbinghub]

Hello! For code reference, I'm living in Pierce County, WA. I have appreciated all of the advice/information I've read so far. I took the liberty of mirror-flipping the attached photo and adding the toilet with a vent to show my situation. Sorry for the long post.

We found significant carpenter ant damage and have been undergoing some renovations in this area. We moved our washer and dryer into the half bathroom to fix some issues where they were backing up at the previous location (placed there during a quick flip). In my photo, you can see that there is a 1.5" pipe coming up from the slab to the left of where the water closet goes. With the washer discharge hose hooked into the 1.5" drain, we have had no backing-up issues, but I know it isn't code to have a washer and sink drain to a single 1.5" pipe. My husband and I prefer not to hook the hose over a utility sink to drain.

This area was originally a garage/shop built between 1964 and 1967, converted to livable space in the 80s.

QUESTION:

If the window is moved, can the WC vent pipe be used if we tie in at 42" or above? I have seen conflicting information about this.

A new 2" drain would be placed similar to what is shown for both the washer and sink. This drain would tie into the WC drain after the vent and before the current clean out, buried just outside, further leading to the septic tank pump basin.

You can tie into the WC vent pipe at 42 inches or higher, as long as it's 6 inches above the highest fixture's overflow level (like your washer or sink). It’s generally okay to combine the washer and sink drains, but the washer needs a 2-inch pipe because of its large water output. This new drain should connect to the WC drain after the vent, and make sure the washer has its own P-trap to stop sewer gases. Always check local codes or ask a plumber to ensure everything is up to code, especially with septic systems.

 

[NurseJenny360]

Thank you both for answering! This clears up a lot of confusion for me and helps moving forward. I really appreciate the explanations.

-Jenny

 

[foplumbing]

the washer needs a 3" drain per code (IPC)
i would assume UPC is the same

 

[Reach4]

the washer needs a 3" drain per code (IPC)
i would assume UPC is the same

This is a rare area where the UPC is more permissive.

 

[wwhitney]

i would assume UPC is the same

It is not.

the washer needs a 3" drain per code (IPC)

Well, IPC 406.2 does require that the standpipe fixture drain connect to a 3" branch drain or stack, but the fixture drain itself may be 2". I agree that this section would require the lav stack to be 3" in the "proposed" diagram, as the standpipe fixture drain is joining the lav stack.

However, as far as I can see the comparable section of the IRC plumbing requirements is P2718.1, which does not imposed this requirement for a 3" branch drain or stack. So if a single family or two family dwelling's plumbing is governed by the IRC P chapters rather than the IPC, then there's no issue. Per the scope sections in Chapter 1 of the Florida Building Code and Florida Building Code, Residential, that is the case in the state of Florida.

Cheers, Wayne

 

[foplumbing]

This is a rare area where the UPC is more permissive.

gave me some homework to do.
i noticed both their Chapter 4 relates to fixtures and UPC specifically does not have clothes washer (wherein which the IPC demands 3")
I did find an illustration on UPC that clearly shows 2" horizontal drain for clothes washer.

I am not sure why IPC would be more strict on this or why 3" is needed at all

 

[foplumbing]

However, as far as I can see the comparable section of the IRC plumbing requirements is P2718.1, which does not imposed this requirement for a 3" branch drain or stack. So if a single family or two family dwelling's plumbing is governed by the IRC P chapters rather than the IPC, then there's no issue. Per the scope sections in Chapter 1 of the Florida Building Code and Florida Building Code, Residential, that is the case in the state of Florida.

I am not following. Why would it be 2" on residential? I don't see why we would ignore the rule in IPC if the IRC doesn't address it

 

[wwhitney]

I am not following. Why would it be 2" on residential? I don't see why we would ignore the rule in IPC if the IRC doesn't address it

In many (all?) states (including Florida) that have adopted the IRC's plumbing chapters, single and two family residences may or must follow the those chapters. In which case the IPC does not apply to single and two family residences at all.

Cheers, Wayne

 

[2stupid2fixit]

If I understand what is going on with my current plumbing, I have a straight pipe in the slab that connects to the main septic drain pipe after the toilet vent. I dug out that area and took a picture for reference.
View attachment 101135

I'm not a great artist, but here is an attempt to draw what I am asking. Washer and lav would have their p-traps but would be wet-vented. Then, they would dry-vent to the current 2" vent for the toilet. The drain would connect to the septic drain outside similar to how it currently is but I would change it to a wye with a 2" instead of the current cast iron 1.5".
View attachment 101136

In my drawing, I think I made a mistake in that I would need to connect the washer and laundry vent before the horizontal portion connects to the vent stack. Correct?

I'm not 100% against adding a separate vent for the washer and lav because I will need to add one for a fan, but I was hoping to vent the fan through the soffit to avoid additional holes in the roof, or the top plate of the wall.

as long as your vents don't allow a forward surge of wastewater to create vacuum, it shouldnt be a problem. forced water will create suction, so just make sure there is no opportunity for the force of the water to create negative pressure (i.e. suction) where you don't want it.