Small Cabin Rough In for DWV - Am I On The Right Track?

[wwhitney]

I posted the wet venting rules from the Canadian code earlier in the thread along with the diagram showing the kitchen sink coming in upstream of the WC. It says under the wet venting rules that "water closets are installed downstream of all other fixtures". The way it reads makes it seem to me that this applies even in the case of the separately vented washer. There are a few other examples provided, but none of them have anything come in downstream of the WC.

OK, I reviewed what you posted. 2.5.2.1(d) refers to the wet vent section only, and does not apply to the drain downstream of the wet vent section. Also, subsection (f) limits the hydraulic load of separately vented fixtures draining through the wet vent to 2 fixture units, so what is the hydraulic load for your laundry standpipe? The code I am under assigns 3 DFUs to a laundry standpipe, in which case the standpipe would be required to come in after the WC. In any event, it will be better to move it to after the WC.

Cheers, Wayne

 

[Jedrek4680]

That looks good only 2 things . Personaly I prefer on the waste stack a 3x3x2 wye for the kitchen , but if the double fitting is available and you like it great its legal ! But the venting for the shower should not be 90s but 2 45s is perfect. Ive Used 90s a million times but for us in upc code its a judgement call and we can get shot down, even though if "nesesary" an inspector can aprrove the 90s

The double sanitary tee is available here and mentioned in Canadian code. The 3x3x3 tee with 2" side inlet is also available but I don't see reference to it in our code.

For the main stack where the shower vents, 2 90s will keep it up higher in the floor joist so in that application I think it is "necessary" to prevent freezing. Nobody will be inspecting since I am building in an unorganized township so it is up to me to pick the lesser of 2 evils (being sharper bends or further from the inside of the thermal envelope).

 

[Sponsor]

 

[Jedrek4680]

OK, I reviewed what you posted. 2.5.2.1(d) refers to the wet vent section only, and does not apply to the drain downstream of the wet vent section. Also, subsection (f) limits the hydraulic load of separately vented fixtures draining through the wet vent to 2 fixture units, so what is the hydraulic load for your laundry standpipe? The code I am under assigns 3 DFUs to a laundry standpipe, in which case the standpipe would be required to come in after the WC. In any event, it will be better to move it to after the WC.

A clothes washer is listed as 2 fixture units by our code, requiring a 2" trap. A kitchen sink (as shown in the code example) is 1.5 fixture units. So, I think the clothes washer is an acceptable substitute for the kitchen sink which was used in the code example, but I could not run both into this wet vented branch.

 

[wwhitney]

For the main stack where the shower vents, 2 90s will keep it up higher in the floor joist so in that application I think it is "necessary" to prevent freezing.

(2) 45s would definitely be better, we may be able to figure out something. You say there's a 4 ply beam supporting the floor joists under the exterior wall. What is the height of the floor joists, and in the dimension parallel to the joists, what are the relative locations of (a) the inner face of the beam, (b) the inner face of the rim joist and (c) the inner face of the wall plate?

Cheers, Wayne

 

[wwhitney]

A clothes washer is listed as 2 fixture units by our code, requiring a 2" trap. A kitchen sink (as shown in the code example) is 1.5 fixture units. So, I think the clothes washer is an acceptable substitute for the kitchen sink which was used in the code example, but I could not run both into this wet vented branch.

OK, so it's not required to move the laundry to after the WC, but it's also not prohibited. You can do it without drilling any joists: just drop the drain to below the floor joists, farther enough away from the horizontal WC/lav drain so that when you turn at a 45 towards the stack, you pass on the left side of the vertical WC fixture drain, and can hit a wye downstream of the WC combo.

[And if you want, you can similarly tie in the WC with a wye, by turning the 90 below the closet flange 45 degrees towards the stack.]

Cheers, Wayne

 

[Jedrek4680]

(2) 45s would definitely be better, we may be able to figure out something. You say there's a 4 ply beam supporting the floor joists under the exterior wall. What is the height of the floor joists, and in the dimension parallel to the joists, what are the relative locations of (a) the inner face of the beam, (b) the inner face of the rim joist and (c) the inner face of the wall plate?

The floor joists are 2x12s so the actual dimensions are 1.5" x 11.25".
The rim joist sits directly over the outside ply of the 4-ply 2x12 beam.
So, on the inside of the rim joist, there are 3 plys worth of 2x12 beam to get around (3 x 1.5" = 4.5")

So using the outside sheathing as a reference point
a) the inner face of the beam is 6" inside of the sheathing (or 4.5" inside from the inner face of the rim joist"
b) the inner face of the rim joist is 1.5" inside of the sheathing
c) the inner face of the sill plate is 5.5" inside of the sheathing (2x6 studs)

 

[wwhitney]

Then I'm 95% sure you have enough height to put the shower san-tee under the wall plate, with a street 45 on the outlet to clear the corner of the 4-ply beam before the drain drops below the bottom of the joist, then another 45 once you are clear of the beam to go back vertical.

Cheers, Wayne

 

[Jedrek4680]

Then I'm 95% sure you have enough height to put the shower san-tee under the wall plate, with a street 45 on the outlet to clear the corner of the 4-ply beam before the drain drops below the bottom of the joist, then another 45 once you are clear of the beam to go back vertical.

Okay, makes sense and keeps the shower trap up high. It would be like this but with 45s bringing the shower vent / main stack and kitchen drain down below the joists.

For the washer drain, why is it not prohibited to bring it in down stream of the WC? Is it because the portion downstream of the WC is not serving as a wet vent for the washer since the washer is individually vented?

Is there a functional benefit to tying the washer in downstream of the WC?

 

[WorthFlorida]

Here is my favorite plumbing reference. Using the correct elbows, wye's and san-tee's are explained.
Plumbing Guide 2015 - Helpful Hints Residential Construction

 

[wwhitney]

For the washer drain, why is it not prohibited to bring it in down stream of the WC? Is it because the portion downstream of the WC is not serving as a wet vent for the washer since the washer is individually vented?

Each fixture gets a vent connection within the prescribed distance of the trap (or fixture outlet, for a WC). If the vent also receives the drainage of another fixture (allowable if you meet the rules), it's a wet vent. In your diagrams, the only wet vent is the lav drain between the WC connection and the lav vent takeoff (the san-tee the lav trap connects to).

What (d) is prohibiting, for example, is joining the shower trap to the lav/WC drain downstream of the lav and relying on the lav dry vent to also wet vent the shower. The wet vent has to stop at the WC.

Is there a functional benefit to tying the washer in downstream of the WC?

Obviously my plumbing code thinks so, as it prohibits the upstream connection. Clothes washers (and garbage disposals to a lesser extent) are different from other fixtures in that they have a pumped discharge, rather than just relying on gravity drainage. So some plumbing codes apply additional restrictions to them.

Cheers, Wayne

 

[Jedrek4680]

Each fixture gets a vent connection within the prescribed distance of the trap (or fixture outlet, for a WC). If the vent also receives the drainage of another fixture (allowable if you meet the rules), it's a wet vent. In your diagrams, the only wet vent is the lav drain between the WC connection and the lav vent takeoff (the san-tee the lav trap connects to).

What (d) is prohibiting, for example, is joining the shower trap to the lav/WC drain downstream of the lav and relying on the lav dry vent to also wet vent the shower. The wet vent has to stop at the WC.

Obviously my plumbing code thinks so, as it prohibits the upstream connection. Clothes washers (and garbage disposals to a lesser extent) are different from other fixtures in that they have a pumped discharge, rather than just relying on gravity drainage. So some plumbing codes apply additional restrictions to them.

Cheers, Wayne

This all makes sense, thanks for the help to interpret and clarify these points.

Now I need to figure out how to draw 45s and then what order to assemble everything so I don't get stuck.

Thanks so much for all the guidance!

 

[Jedrek4680]

Here is my favorite plumbing reference. Using the correct elbows, wye's and san-tee's are explained.
Plumbing Guide 2015 - Helpful Hints Residential Construction

This is a great consolidation of examples... love it

 

[Jedrek4680]

Figured out how to do the 45s so the bends are pretty accurate now, just need to figure out the piping sizes which should be pretty simple with only the WC wet venting... and then make my parts list.

 

[Jeff H Young]

jederek, wouldnt you want that 2 inch (wash machine) tucked up in joist bay? I been asuming you wouldnt want to be below except close to side wall where maybe a basement is getting finished and perhaps soffit. any way looks good again and I agree the function may be more reliable dont want any gurgling at the w/c do we a little extra precaution is good

 

[Jedrek4680]

jederek, wouldnt you want that 2 inch (wash machine) tucked up in joist bay? I been asuming you wouldnt want to be below except close to side wall where maybe a basement is getting finished and perhaps soffit. any way looks good again and I agree the function may be more reliable dont want any gurgling at the w/c do we a little extra precaution is good

There won't be a basement below, the closest I would get would be boxing in the plumbing with PT plywood and insulating it. So, ideally the washing machine would be tucked up in a joist bay but then cannot vent after the WC unless I drill 2 joists. and use a long sweep 90 instead of the 45 that moves it to the left.

I am thinking with a washing machine it drains a large quantity of water at once so it would be less susceptible to freezing that something like the kitchen sink where it is used more frequently for smaller quantities of water. But, maybe for a small 2" pipe, keeping it tucked up is better.

 

[Jedrek4680]

Tucked the washer drain up as well now. Can it wye into the horizontal main drain like that?

 

[wwhitney]

Can it wye into the horizontal main drain like that?

Yes, that's fine. If you route the laundry drain towards the beam first, and then above the 3" drain, you can replace the last 90 bend with a 45, but I guess that's not a particular improvement.

Your last drawing has the advantage that all the below joists drains are in a single 8' line, which would simplify insulating them if desired.

The US building code would let you prescriptively drill up to a 3.75" hole through a 2x12. So if you wanted to tuck everything up into the joists, you'd only have to drill (2) joists for the 3" WC drain, and (3) more joists for a 2" or smaller drain. [If your stack location is flexible, you could move it over two joist bays and avoid drilling any joists for a 3" drain.] You'd just have to adjust your shower venting.

Cheers, Wayne

 

[Jedrek4680]

Yes, that's fine. If you route the laundry drain towards the beam first, and then above the 3" drain, you can replace the last 90 bend with a 45, but I guess that's not a particular improvement.

That'd save drilling 2 joists but I think it would push the main 3" pipe down a little further towards the ground, plus leaves more piping exposed if I do not box below the joists.

Your last drawing has the advantage that all the below joists drains are in a single 8' line, which would simplify insulating them if desired.

Yup, I like simple.

The US building code would let you prescriptively drill up to a 3.75" hole through a 2x12. So if you wanted to tuck everything up into the joists, you'd only have to drill (2) joists for the 3" WC drain, and (3) more joists for a 2" or smaller drain. [If your stack location is flexible, you could move it over two joist bays and avoid drilling any joists for a 3" drain.] You'd just have to adjust your shower venting.

Our code here in Ontario only allows a 2.75" hole drilled in a 2x12. Plus I am near the span limit of 2x12s as floor joists and there is a stacked washer/dryer and propane stove and kitchen cabinets all at midspan so I prefer not to weaken those joists if possible and practical. I can live with the 2 smaller holes for the 2" washer pipe to get across. Keeping the main 3" pipe below the joists also makes cleanout access very easy.

The stack location is pretty much fixed as I am trying to keep it as far to the left as possible. Reason being I am located back far enough off the main road that the cost of having grid power is not really practical so we'll be using solar and I want to keep the vent off to the side as much as possible.

 

[Jeff H Young]

Unless theres a real issue/ reason A few 90s is no big deal and Im not going through any joist or stud on a 45. I do like jumping into joist bay but if it was a crawl space I wouldnt bother drilling any joists it would be hanging . A lot of thought going into this which is good I see this little job functioning perfect for decades 50 plus years. and why not do it right just a little thought goes a long way and Jederek and Wayne you guys are keepping me thinking about ways to do things make it better and ballancing between what wont improve things or whats overkill, and a lot are just owner preferance .

 

[wwhitney]

That'd save drilling 2 joists but I think it would push the main 3" pipe down a little further towards the ground, plus leaves more piping exposed if I do not box below the joists.

That's another option, I was thinking about still drilling the joists, just over the 3" main drain.

Our code here in Ontario only allows a 2.75" hole drilled in a 2x12.

Interesting to know. Have you considered I-joists?

Cheers, Wayne