Can I tie a washing machine into a bathtub drain line?

Users who are viewing this thread

Jonathaninsc

New Member
Messages
1
Reaction score
0
Points
0
Location
South Carolina
Is there any reason I would not want to tie a new washing machine into a bathtub drain as long as I give the washing machine its own P trap? One plumber I spoke with was concerned the force of the washing machine "would suck the water right out of the trap" of the bathtub. Does that sound right? The washing machine is a high efficiency model and uses very little water. Also, can I use an AAV to vent the washing machine?

Thanks!
 

Jadnashua

Retired Defense Industry Engineer xxx
Messages
32,771
Reaction score
1,191
Points
113
Location
New England
EACH trap needs its own individual vent. A tub drain might be as small as 1.5". A washing machine drain needs to be at least 2". So, probably not, but it would depend on how things are layed out. If each trap is properly vented, then, no, neither should siphon the other. Some places do not allow an AAV, so even if it might work, it would not be to code. It is always better to do an atmospheric vent if possible. Keep in mind that an AAV can only let air in, and depending on where it is, sometimes air needs to come out as well.
 

Gary Swart

In the Trades
Messages
8,101
Reaction score
84
Points
48
Location
Yakima, WA
I believe the question of AAV on a washer was addressed recently, and if I remember correctly, the can not be used for the reason Jim noted on an AAV only letting air in. Also as noted, washers now require a 2" drain.
 

Terry

The Plumbing Wizard
Staff member
Messages
29,946
Reaction score
3,460
Points
113
Location
Bothell, Washington
Website
terrylove.com
Is there any reason I would not want to tie a new washing machine into a bathtub drain as long as I give the washing machine its own P trap?

It's more about the venting.
Your plumber has mentioned that water from the washer discharge will suck the tub trap dry.
If you were to go downline of the tub line, after it has been vented, and then branch off the 2" waste line, with an above floor trap and vent for the washer, that would work. The two should work independent of each other.

A washer discharges with a pump. Some locations require a 3" line after the 2" trap and trap arm.
 

JohnfrWhipple

BATHROOM DESIGN & BUILD
Messages
3,225
Reaction score
102
Points
48
Location
North Vancouver, BC
It's more about the venting.
Your plumber has mentioned that water from the washer discharge will suck the tub trap dry.
If you were to go downline of the tub line, after it has been vented, and then branch off the 2" waste line, with an above floor trap and vent for the washer, that would work. The two should work independent of each other.

A washer discharges with a pump. Some locations require a 3" line after the 2" trap and trap arm.

Terry is there not also a certain fall that needs to be realized? I think its something like 36".

JW
 

Jadnashua

Retired Defense Industry Engineer xxx
Messages
32,771
Reaction score
1,191
Points
113
Location
New England
There's a minimum height of the standpipe, but that is separate from any normal slope once it hits the drain. That height varies based on your local codes.
 

JohnfrWhipple

BATHROOM DESIGN & BUILD
Messages
3,225
Reaction score
102
Points
48
Location
North Vancouver, BC
There's a minimum height of the standpipe, but that is separate from any normal slope once it hits the drain. That height varies based on your local codes.

It's the vertical drop of the stand pipe. I think it needs 36" of drop before hitting the PTrap. What is the requirement in New England?

JW
 
Top
Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.

If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.
I've Disabled AdBlock    No Thanks