Help! I have little space between my drain pipe and the top of my counter top. How can I get a few e

[Sbas]

I am in the process of building a tiny house on wheels and just had my plumber finish the drain line. Because we needed to achieve minimum slope downhill, my drain pipe ended up being a bit higher than I wanted. I know have very limited space to work with my kitchen sink.

Here is a picture of my setup http://imgur.com/a/myDkm

Some important things to know.

1) The bottom of the window sill plate is at 44 inches

2) There is only 13 1/2" from the center line of the waste to the bottom of the window sill plate

3) I am taller than the average person, so I am aiming to have the sink.counter at 39" or 40" but anything taller, is too high.

4) If I go with a 40" counter, I believe I only have 9 1/2" for the sink, basket drainer and tail piece combined. This would be to achieve a 1/4" slope from bottom of basket strainer to drain pipe.

Questions I have:

1) What is the minimum clearance I can do from bottom sink strainer to the center of the waste/drain pipe entering the wall? I've seen 4" but I've also seen you only need 1/4" slope per foot (which would only mean I need to be ~ 1/4" higher.

2) Is there any solution to bringing the drain hole (that connects to wall) lower to where the red circle is? Perhaps a different fitting or just skip the 90?

3) I plan to cut the tail piece to the shortest possible to save space for counter depth. What is the minimum I can do?

Any other tips to give me a few extra inches would be much appreciated. I would REALLY like to have a 9" deep sink, which would put my 12 or 13" with basket strainer and tail piece as well, but I would live with 8".

Thank you so much!

 

[Wrenched]

Sounds like a really tight space to make work. Tiny, even. Is the house on wheels? Is it going to be inspected?

There are a couple different things that can be done.

First, the drain can be re-piped to look a little something more like

http://inspectapedia.com/plumbing/1623s.jpg

Note the minimum and maximum distances. Remember to keep the AAV accessible - they do fail over time (Was there no way to properly vent the sink?). This should give you roughly two inches.

Second, you can get a shallow basket strainer, and ditch the tail piece for an ABS swivel adapter. These two things might buy you an inch and a bit off of other options. You're still looking at about 12" from top to drain c/l for a 9" deep sink (maybe slightly less if you can fit the p-trap in using a FPT x spigot swivel adapter).

I also suggest thinking about what your access is for cleaning the pipe in the future.

Good luck!

 

[Sponsor]

 

[Sbas]

Hey Wrenched,

Thank you for the help!

Yes - this is a tiny house and wheels actually. And no, it will not be expected and we are building pretty much everything to code (but would probably be ok doing something different for this situation if its what I have to do).

So for the minimum distance from the AAV vent to the end of the trap weir, I will need 3 inches (1.5" diameter x 2)? And is the trap weir just where water does not sit in the p trap or is this a separate fitting?

A few other questions
1) Is it better to get the studor redi-vent rather than your basic aav vent (like I have on now)?
2) How would moving my aav vent give my 2 inches extra to fit a sink)?
3) Shallowest basket strainer I have seen is 2 1/4". Have you seen anything less?
4) Someone else suggested to eliminate the san tee and just put a 90 directly to the pipe (where the red circle is) and turn it inwards towards the wall. What do you think about that? Would that be enough drop?
5) The big question is what the minimum slope/clearance I need to meet from the bottom of the basket strainer (or is it bottom of tail piece?) to the drain pipe in wall?

 

[Reach4]

The bend at the red circle supposed to be a long sweep for house codes. I understand that makes things worse for you. That fitting is where a clog would be most likely -- where you transition from vertical to horizontal. Consider adding a cleanout that you could use.

It may be hokey, but if you cut the pipe a little above the santee, you could put a banded rubber coupler there. That would let you use the cut as a cleanout, and it would let you pull the pipe with the AAV to replace the AAV. I am not a plumber.

 

[Sbas]

I see. so Is a minimum 90 degree needed there to give it a vertical drop, before the horizontal drop?

To be clear, you are saying it would not be advisable to lower the drain hole any lower (with this current setup)?

 

[Reach4]

I see. so Is a minimum 90 degree needed there to give it a vertical drop, before the horizontal drop?

I don't understand. If you could use 45s, that would be good, but I don't think that is what you are saying. Maybe you are asking if there is a santee where the exit comes off at an angle, or if you could tilt your santee 22.5 or 45 degrees to give you an early start to hitting the horizontal? I am not a plumber, but I would suspect yes, but I don't know. I am confident that the 45 would be fine at the bottom, but could the santee be rotated this much?

To be clear, you are saying it would not be advisable to lower the drain hole any lower (with this current setup)?

I would say that, unless you could lower the pipe leaving to the right.

 

[Wrenched]

Hello sbas,

I think throwing together some dimensioned drawings might help us be sure we're talking about the same things.
I'm away from my computer, but hopefully this sketch will be clear.

The proposed piping layout is probably the more common way of piping a kitchen sink. The challenge will be getting the horizontal section to fit, and keeping the AAV accessible.

Q's: 1) Studor is considered a higher quality AAV, though AAVs in general are imperfect solutions to a problem with better, but more expensive, solutions. They are generally not accepted here unless there are not other reasonable solutions.

2) as per the sketch, it's not so much about moving the AAV as about moving the trap arm connection.

3) 2.25" is about as shallow as a basket strainer gets without going to a flat top style or getting a custom build.

4) this sounds like the proposed solution in the sketch.

5) you can probably get quite close to 0.

If you're not being inspected (by a strict inspector at that), as long as the horizontal drain is not flat or backgraded, you can push slightly less than 1/4" per ft slope. Minimum grade is a good idea that looks to keep flow characteristics optimal. 3/16" slope, or even sections of 1/8" slope, will not suddenly prevent drainage, it will just require more frequent cleaning. Maybe every ten years instead of every twenty, depending on effluent contents.

As Reach4 points out, the close radius 90 degree elbow is not to code in most jurisdictions (two 45s is commonly the way to take a 90degree turn). It would work, but causes enough issues to be disallowed by code.

Will the house use a holding tank, or will it be piped to a sewer at location of use?
I'd love to see the layout of the tiny house, it sounds interesting.

 

[Reach4]

"Proposed" looks optimal to me.

 

[Sbas]

Hi Wrenched,

Sorry for the late reply. So I did get the same advice from another plumber as you gave. He mentioned that I should use a long turn 90 elbow. See "How to santee" diagram I attached. I'm assuming the long turn is to give a better drainage path.

So this will not meet code, but will be sufficient?

1) For the clearance from the bottom of the strainer to center of waste pipe, does code call for minimum clearance? I am seeing 4" on some diagrams online but I have also hear 1/8" will do.

2) When i read about the needing to below the top opening of the vent, does that mean the very top of the sanitary tee?

3) I plan to remove the AAV vent and move it to under the sink like the image I posted below. Will that work ok?

4) Can all of my pieces be 1 1/2"? I thought I was reading somewhere that the 90 needs to be 2" or something.

The drainage will be a grey water and will have no disposal,

I would love to show you the layout of my tiny house! Perhaps you can message me your email?

 

[Wrenched]

Hey sbas,

My code will be somewhat different from yours, which I think is based on the UPC, but I don't see any conflict between the code and the pictured solution(it should be to code). The long turn 90(two 45s are often used) absolutely creates better flow characteristics as well being easier to run cleaning equipment through.

1) as far as I can tell your code does not specify a minimum distance for a fixture outlet pipe. A closer look at the UPC has been on my to do list for a while though.

2) Do you have context for this? Clearly the vent must be above the drainage system. Best practices used to be to install above flood level rim of the fixture served, though most installation instructions now say 4-6" above trap arm.

3) yeah, that looks like a way to do it. Just avoid crown venting but within 6' of the trap and keep the AAV accessible.

4) any context for this? There is no issue with increasing the size of a pipe, though no reason to do so here. Reducing the size of a drainage pipe is not allowed.

So it will drain to a grey water tank?

I got your PM. I look forward to seeing the pics!

 

[Sbas]

Great! So any benefit using to 45's vs one long turn 90?

So will I be ok with ~1/2" basket strainer above waste?

I'm trying to do a mockup this weekend to see how deep of kitchen sink (drop in) can get away with. If the very top of my counter is at 39" and have 12.5" inches from top of counter to middle of waste pipe

I'm pretty positive I can easily do a 8" depth sink if I used a 2.25" basket strainer and cut my tailpiece to ~2". This would give me 1/2" space above the waste line. Does that sound about right to you?

And grey water I am still researching but most likely will drain into the ground. Any recommendations?

 

[Wrenched]

Not really. Long-turn 90s are slightly better in a lot of cases, if the inspector will accept them.

As long the bottom of the basket strainer is above the top of the trap arm it should be fine, though drain time may be affected.

Again, I'll point out using a tail piece is not required, though the numbers look like they have enough flexibility to work a few different ways.

Wow, greywater disposal is a whole other issue and varies a huge amount from jurisdiction to jurisdiction. Is your blackwater connected to a sewer? Is this to be a semi-permanent installation?

Usually you'll want a greywater filter box (something to intercept organic material and detergents) and some flavour of dispersal field or drywell.

 

[Sbas]

Ok perfect. I am building to code in almost everything in the tiny house, but am not being inspected. So this will be ok as long as it functions properly.

Ahh yess, I missed that you said I can ditch the tail piece. Is this the right swivel adapter I need? http://www.globalindustrial.com/p/p...wivel-tray-plug-adapter-w-washer-spigot-x-npt

And is the sole purpose of a tailpiece JUST to allow more vertical drainage?

I notice that without a tailpiece, I will have no flanges around the top - is that fine?

And if I do decide to use an abs tailpiece, what is the minimum height I could do to allow the nut to screw up as much as needed? If I do use a tailpiece was thinking of cutting it down to 1.5".

No blackwater. Composting toilet

 

[Terry]

The AAV must be accessible for air intake and for replacement. It makes the most since with your grade issues to not use a 90 to turn up. There is no point in doing that if it's too high already. The vent just needs to be within 42" of the trap and coming off at either the top of a santee, or if the line is horizontal, a wye fitting. Not being inspected I don't see an issue with the santee though on the horizontal.