Water Softener Draining Question

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Ashton

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This is less a water softener question and more a plumbing question, so I think it belongs in this subforum. Apologies if I'm wrong.

I'm trying to kill two birds with one stone, but want to make sure I'm doing it all right. My two issues are:

  1. Poor water softener drainage
  2. Lack of a utility sink in the laundry room.
I'd like to install a sink and drain the water softener into said sink, but ideally I'd like to avoid dumping brine water directly into the sink body for both maintenance and usability reasons. Instead I'd like to dump the brine water into the plumbing under the sink, which is where the problems start. Before cutting into plumbing I have two important questions:

  1. Can I plumb the drain line into the plumbing under the sink and above the p trap (I plan to use this airgap), or do I need a separate p trap for the drain line?
  2. The horizontal run of this drain line needs to pass through the stud bay that the dryer vent is in. I think I can relocate the dryer vent hole to be higher in the wall to make room, but are there any limits on how close PVC can get to a dryer vent?

Current Condition
original.jpg

Single P trap (washing machine outlet excluded because I'm a slow drawer)
single p trap.jpg

Double P trap
double p trap.jpg

Edit: I saw in another thread about tying the utility sink into the washing machine stand pipe rather than the vent. I don't think this will work in my case purely because of positioning. The planned location for the utility sink is greater than 30" from the laundry stand pipe, but a mere 3' from the vent stack. I think this makes tying into the standpipe a no-go, but should be okay for tying into the vent with a separate P trap.
 
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Ashton

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Reading the Idaho State Plumbing Code, I believe that tying into this vent stack would technically create a vertical wet vent, which is allowed in my area as long as it's below 6' in length (908.1), but now I'm wondering if I should just add an AAV (allowable in Idaho) just to be safe.
 

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Can I plumb the drain line into the plumbing under the sink and above the p trap (I plan to use this airgap), or do I need a separate p trap for the drain line?
Most places would allow a branch tailpiece below the drain basket. The air gap would feed the "branch" input.
The horizontal run of this drain line needs to pass through the stud bay that the dryer vent is in. I think I can relocate the dryer vent hole to be higher in the wall to make room, but are there any limits on how close PVC can get to a dryer vent?
I certainly would not want pvc to touch my dryer vent. I don't know what kind of separation would be needed, but I would think some kind of metal that provides a space between the two would be good.

For adding the softener drain to the laundry standpipe, there are air gaps made for the purpose. There are different choices depending on whether this is an old 1-1/2 inch standpipe or a 2 inch standpipe. This would typically be the easiest solution.
 

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Okay, here's my updated design, which I think is close to correct. I found a straight edge, but alas it can't help my handwriting out.
updated design.jpg



  1. The vent pipe is 2", which according to the code should be able to vent 16 units. The vent only serves the laundry room.
  2. The sink drain pipe will be 1 1/2", which permits a maximum distance between trap and vent of 30". Placement will be damned close to 30" as is, so I'll play it safe and add an AAV. An Oatey 8DFU unit should more than suffice, and I can place it in a serviceable location under the utility sink,
  3. Even without an AAV this is a short vertical vent, and Idaho code allows one to be up to 6' tall, so I would be okay as long as the horizontal run between the utility sink trap and the vent is less than 30".
  4. It seems like this room will only have 4 DFUs, 2 each for the utility sink and the washing machine. I didn't see water softeners listed in the appropriate table, so I assume that they're worth 0 DFUs? If they're > 0, I'll need to change out the drain on the sink from 1 1/2" to 2", since according to code it'll only handle 2 DFUs.
I think that's all correct, did I mess anything up?

I certainly would not want pvc to touch my dryer vent. I don't know what kind of separation would be needed, but I would think some kind of metal that provides a space between the two would be good.

I'll call and ask the inspector, since they're pretty easy to contact here. I happen to have one of these laying around, it should provide a lot of air and steel between the PVC and the dryer hose. if that's not good enough then I'm kinda up the metaphorical creek on this project.

For adding the softener drain to the laundry standpipe, there are air gaps made for the purpose. There are different choices depending on whether this is an old 1-1/2 inch standpipe or a 2 inch standpipe. This would typically be the easiest solution.

I'm already having some drainage issues due to the distances and elevations involved. Given that I want to install a utility sink anyways, I figured it would be best (and cleanest) to reduce the distance that the discharge has to go through in that 1/2" tube.
 

Reach4

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Idaho appears to be similar or based on UPC. There may be a relevant amendment, but if not, no AAV allowed.

https://dbs.idaho.gov/programs/plumbing/#

From a non-code consideration, if you build what you drew, you would want the standpipe top to be higher than the flood level of the sink. That way the sink would add some buffering.

The following picture is based on IPC, not UPC. But from a functionality point of view, it could be of interest.

index.php
 

Ashton

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Idaho appears to be similar or based on UPC. There may be a relevant amendment, but if not, no AAV allowed.
https://dbs.idaho.gov/programs/plumbing/#

From a non-code consideration, if you build what you drew, you would want the standpipe top to be higher than the flood level of the sink. That way the sink would add some buffering.

The following picture is based on IPC, not UPC. But from a functionality point of view, it could be of interest.

index.php

Idaho's code is modified to allow AAVs in some use cases. Here's the relevant section (emphasis mine).
Parameters for the limited use
of Air Admittance Valves (A.A.V.). (4-2-08)
(a) An A.A.V. may be used only in residential
buildings. (4-2-08)
(b) In remodels, an A.A.V. may be used with island
fixtures or remotely located sinks such as in bar,
kitchen, or laundry tray locations. An A.A.V.
shall not be used in bathroom groups.
(4-2-08)
(c) In new construction, an A.A.V. may be used on
island fixture sinks. (4-2-08)
(d) Each A.A.V. may be used to vent only one (1)
floor. (4-2-08)
(e) Each A.A.V. must be readily accessible. (4-2-
08)
(f) The cross-sectional area of venting must remain
the same and must meet the largest required
building drain. (4-2-08)
(g) An A.A.V. shall only be installed in accordance
with the manufacturer’s installation standards
as per ASSE 1051. (4-2-08)
(h) An A.A.V. may not be used in an attic, crawl
space, outside installation, or in connection with
chemical or acid waste systems. (4-2-08)

The problem I have implementing the design you provided is that my laundry room has a different arrangement. The washing machine standpipe is on the wrong side of the vents (dryer and drain) from where I can put the utility sink, leaving it close to 5' away from the standpipe, much farther than the maximum 30" listed. I really have to go from the utility sink directly into the vent, either with an AAV, a wet vent, or a dry vent tied in 42" above everything else.

From a non-code consideration, if you build what you drew, you would want the standpipe top to be higher than the flood level of the sink. That way the sink would add some buffering.

That's a really good call out, thank you.
 

Reach4

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The problem I have implementing the design you provided is that my laundry room has a different arrangement. The washing machine standpipe is on the wrong side of the vents (dryer and drain) from where I can put the utility sink, leaving it close to 5' away from the standpipe, much farther than the maximum 30" listed. I really have to go from the utility sink directly into the vent, either with an AAV, a wet vent, or a dry vent tied in 42" above everything else.
Given that you can use the AAV, I expect one of the people proficient in UPC will have a suggestion. Worst case you could have a standpipe trap and a sink trap, each with their own AAV or shared by combining them 6 inch above the flood levels. But there may be something like vertical wet venting that will do the job for you.

UPC has some limitations on how close to the floor the trap must be for a laundry standpipe. But a standpipe dedicated to a softener drain probably gets more leeway.
 
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