AC/ condensate drain line. What is this mystery pipe?

[Donn2390]

I'm having my master bath remodeled and in doing so we pulled out the old double sink vanity yesterday. Under the sink on one side there is a 3/4 inch PVC pipe coming out of the wall near the drain pipe. There is a short pipe, about five inches in length, connected between the sink drain line and the P trap. That short pipe has a 3/4" Tee with a black hose connected between the PVC pipe and the Tee. The pipe coming from the wall has a very slow drip which drains into the drain line via the hose. I think it might be a condensation line from the A/C or ?? I asked at the local hardware store while purchasing a new angle stop valve, and was met with a blank stares. I looked under the sink of my neighbor's identical home and there is no such pipe.
I placed a container under it for now, but it will be at least a week before the new vanity is installed and plumbed. In the mean time it fills a small trash can in 4-5 hours. Today I plan to buy a longer hose to temporarily connect the PVC pipe directly to the drain line so I don't have to be emptying buckets for the next week or so.
Please educate me, where is this pipe coming from and what is the purpose?
Thank you......

 

[Donn2390]

Pictures do help a lot

 

[Sponsor]

 

[Donn2390]

You want pictures, ya got pictures...! You already knew I'm not a plumber, now you know I'm not a photographer either...!!
The PVC pipe is stubbed about three inches out of the wall. I added the 90 and extension so that I could run the hose back to the drain.
That cute little black pipe in the first picture is obviously a standard part that was purchased, not something Jerry rigged, however I think the whole thing is Jerry rigged. Why doesn't the identical home down the block not require it???

 

[James Henry]

Hook a wet vac up to one end and check the other end for suction.

 

[Donn2390]

Hook a wet vac up to one end and check the other end for suction.

If I knew where the other end of the pipe was, I wouldn't be asking what might be the purpose of the pipe. It's just a 3/4" white PVC pipe stubbed out of the wall and connected into the sink drain line. It can and will be re-plumbed the way it was when I took it apart, and my life will continue on without incident, but it's the curiosity factor that makes me ask what the purpose could be. I have never seen anything like that before in my semi limited amount of plumbing experience.
As I mentioned, I looked at the identical home a couple of doors down the street, built by the same builder at the same time and that pipe doesn't exist...
Inquiring minds want to know........

 

[Gsmith22]

only time I have ever seen 3/4" PVC used is for condensate drain lines on HVAC equipment. I am not a professional plumber so I'm sure there are other uses. Do you have any HVAC units vertically above this area like in an attic?

 

[Reach4]

only time I have ever seen 3/4" pvc used is for condensate drain lines on HVAC equipment. I am not a professional plumber so I'm sure there are other uses. Do you have any HVAC units vertically above this area like in an attic?

Yes, HVAC. But it could have been be a softener drain, were it not for the slow drip consistent with an AC evaporator.

I think that black thing in your photo is a branch tailpiece extension with a nut from a trap around the bottom.

 

[hj]

It is the AC/ condensate drain line. Reconnect it to the new sink drain.

 

[mssonline2019]

I'm having my master bath remodeled and in doing so we pulled out the old double sink vanity yesterday. Under the sink on one side there is a 3/4 inch PVC pipe coming out of the wall near the drain pipe. There is a short pipe, about five inches in length, connected between the sink drain line and the P trap. That short pipe has a 3/4" Tee with a black hose connected between the PVC pipe and the Tee. The pipe coming from the wall has a very slow drip which drains into the drain line via the hose. I think it might be a condensation line from the A/C or ?? I asked at the local hardware store while purchasing a new angle stop valve, and was met with a blank stares. I looked under the sink of my neighbor's identical home and there is no such pipe.
I placed a container under it for now, but it will be at least a week before the new vanity is installed and plumbed. In the mean time it fills a small trash can in 4-5 hours. Today I plan to buy a longer hose to temporarily connect the PVC pipe directly to the drain line so I don't have to be emptying buckets for the next week or so.
Please educate me, where is this pipe coming from and what is the purpose?
Thank you......

Most AC drain lines are located outside, near the condenser unit. Push the stiff, thin brush into the end of the drain line. This might clear any clogs located near the end of the drain line. In most cases, the AC drain line clog will occur farther down and you'll need to do a little more work.Usually seen on most electric air handlers. ... This can cause the water not to drain and can cause overflow problems. A standard residential air conditioning system needs to have a trap of at least 1 1/2 inches to drain properly. There should not be an air vent between the drain pan and the trap.
i hope this will solve your little problem. and i will try with the more help.
Thanks
Nishan Singh

 

[James Henry]

I think it might be a condensation line from the A/C or ??

I assumed you already had an idea. my bad.

 

[James Henry]

It is the AC/ condensate drain line. Reconnect it to the new sink drain.

I agree.