Science (Plumbing) Problem

[Mark1]

OP here. I really appreciate all responses. I'll try to response to your comments, since folks were nice enough to give their thoughts.

If the piping is clogged it is within the wall and not the piping shown in the photo for sure as I have had this piping off numerous times now and it is always clean. Probably should have snaked the piping within the wall when I had the drain piping off, but I didn't. Besides, the only snake I have is really for fishing wires though walls and not cleaning piping.

There are 2 vents above the bathroom that breakthrough the roof and both look like Broan Universal Roof Caps (not round PVC piping). Not sure who goes with what vent, but there is a toilet, a sink and exhaust fan within the room that need to vent somewhere. The plumber will be the one going up on the roof to inspect and not me since I'm getting more scared of heights as I age.

Sounds like the air admittance valve really needs to be higher to work properly. I guess I could run it up behind the corrugated metal wall below the faucet and hide it there, but I really hate to keep going down the admittance valve route as it is not really addressing the root cause of the problem.

I guess in the near future I will remove the air admittance valve tee and put the piping back the way it was originally. While doing this I can easily perform Winemakers bucket test and it might actually test the small strainer hole size theory that NW-Bound highlighted. I actually had the same strainer thought early-on, but I talked myself out of it, when I tried to address 6miths surface tension theory, by adding lots of soap and surfactant within the sink water to help break the surface tension and it didn't help. One data point that does support the NW-Bound's theory is that absolutely no air exist out of the water column within the bucket once it starts to drain fast (no bubbles and no early whirlpool action), which means all the air had to exist down the sewer piping. I have no small straws or tube in the house to try the new straw experiment.

I was looking closely at the seal between the bucket and wood counter top to determine how difficult it would be for me to just change out the drain tail piece to a new tail piece (without the strainer on top) to test NW-Bound's theory. The seal is well under the bucket between the wood and the bucket with a sealant in somewhat of a jerry-rigged manner. Therefore, I think I might just need to commit to a new sink and new counter top with the remodel, which means I can now take my drill and make a rather large hole in the strainer to test the “get the air out” theory. However, I won't perform this test until I'm closer to my remodel date.

I have to agree with Finnsky that it probably time for a new plumber, although, my normal plumber typically solves my problem; shows up the same day; and has not charged me for 2 of the last 3 visits.

I'm tend to be slow and deliberate so I don't have a time table yet, but I will definitely let you all know how this story ends. Thanks for all the help.

 

[JoeWras]

To troubleshoot your issue, remove your under the sink vent, place a bucket under the vent; then try to run your drain/sink with whatever water level you want. If the drain is plugged after your vent, you will get some overflow out of your under sink vent (and into your bucket.) If your drain runs fine, your vent is the issue. If your sink backs up and there's no overflow out the vent (it's lower than the sink drain) then your sink drain has an obstruction.

This is the answer. I'm going to stop reading here because OP needs to do exactly this.

The height of the AAV is specified primarily for overflow control and subsequent fouling. Its actual height won't matter if the drain is working properly. You can't get the AAV any higher anyway. Stop thinking about breaking into your wall and do some testing and rod out the line multiple ways first -- before you get out the jackhammers.

 

[Gumby]

Snakes are cheap, maybe $25 at Lowes. A couple years back, I had to disconnect my bathroom sink at the wall and snake the pipe inside the wall. That was indeed the problem. You should keep snaking until you can feel the snake make a clean break into the main drain pipe. Another thing that helped me was to use a funnel and a hose to pour boiling water into the drain to melt soap scum/grease buildup.

 

[eytonxav]

Venting/drain clog or piping coming off p-trap looks to be going up hill. Since you have not snaked the drain piping in and below the wall, hopefully you do not have a snake coming up through the drain.

 

[ERD50]

OP here. I really appreciate all responses. I'll try to response to your comments, since folks were nice enough to give their thoughts. ....

Sounds like the air admittance valve really needs to be higher to work properly. ...

No. See my post #9, and the link I gave.

Quote:
Originally Posted by Fermion View Post
What the heck is that? You can't vent a trap below the level of the sink!

It appears you can, why do you say you can't? This site shows the air admittance valve installed at about the same level as the OP shows. I don't think that's the problem. The air admittance valve solves the problem of a vacuum from the water flow of a different drain sucking the water out of the trap. Vent or no vent, the drainage should be the same.

https://garynsmith.net/venting-101-air-admittance-valve-pros-cons/

-ERD50

 

[Music Lover]

Maybe it's just the angle of the photo but there doesn't appear to be any drop from the trap to the wall. Might even run slightly uphill which would lead to more back pressure from standing water to overcome

That's the first thing I saw too. In that situation a couple inches of water drains slowly but once there's more water the weight of it overcomes the slope...the exact scenario the OP described.

 

[NW-Bound]

... While doing this I can easily perform Winemakers bucket test and it might actually test the small strainer hole size theory that NW-Bound highlighted. I actually had the same strainer thought early-on, but I talked myself out of it, when I tried to address 6miths surface tension theory, by adding lots of soap and surfactant within the sink water to help break the surface tension and it didn't help. One data point that does support the NW-Bound's theory is that absolutely no air exist out of the water column within the bucket once it starts to drain fast (no bubbles and no early whirlpool action), which means all the air had to exist down the sewer piping. I have no small straws or tube in the house to try the new straw experiment...

I wondered about the slow water drain down my bathtub for a long time too, because the shower wastewater is of course soapy and should reduce the water surface tension. Lifting up the strainer quickly showed me what the problem really was.

Come to think of it, the small plastic straws many coffee shops offer for use as a stirrer would fit through the holes of my bathtub strainer. This shows you that the holes are small, but not that small. Yet, they impede the air from bubbling up to escape.

 

[Music Lover]

I wondered about the slow water drain down my bathtub for a long time too, because the shower wastewater is of course soapy and should reduce the water surface tension. Lifting up the strainer quickly showed me what the problem really was.

Come to think of it, the small plastic straws many coffee shops offer for use as a stirrer would fit through the holes of my bathtub strainer. This shows you that the holes are small, but not that small. Yet, they impede the air from bubbling up to escape.

If a waste line is properly vented (and not blocked) there's no need for air to come up through the drain. If air is bubbling up the drain there's a problem with the vent. In cold climates sometimes the vent on the roof is blocked with snow or ice.

 

[NW-Bound]

If a waste line is properly vented (and not blocked) there's no need for air to come up through the drain. If air is bubbling up the drain there's a problem with the vent. In cold climates sometimes the vent on the roof is blocked with snow or ice.

Yes, and no.

I will need to explain with some drawings, but it takes too much work. It has to do with the air between the strainer and the J trap. The vent people talk about is for the air after the J trap.

If the OP just drills out the strainer at the bottom of his sink bucket, the problem goes away without him having to do anything else.

 

[Winemaker]

I wondered about the slow water drain down my bathtub for a long time too, because the shower wastewater is of course soapy and should reduce the water surface tension. Lifting up the strainer quickly showed me what the problem really was.

Come to think of it, the small plastic straws many coffee shops offer for use as a stirrer would fit through the holes of my bathtub strainer. This shows you that the holes are small, but not that small. Yet, they impede the air from bubbling up to escape.

The vent for your tub is the handle or flipper to drain the tub. It is the one with one or two screws, and sometimes gets "gombed" up with hair, soap, and whatever folks slather on their bodies while cleaning, washing, exfolliating, lubricating, or preserving themselves. If you take the screws out,( be sure to put a rag over drain so you don't drop the screw down the drain) then remove the cover, let the cover and drain rods hang for a few minutes.. This will expose the vent pipe and some crud, Clean well, then take some WD40 and spray down the vent, then carefully spray some water down the vent, this will lube up the crud/hair that is hanging on the drain mechanism. Gently pull the rods and drain stopper that is located down the vent. Have another rag, garbage can or bowl to put the crud into when you get it out. Be careful of nut breaking or bending rods. Clean assembly and re install.

This is one of the preventative steps I do on every apartment turnover, and eliminates any calls as to "my tub won't drain". An ounce of prevention....

 

[jim584672]

My guess is it needs snaking. I bought one that attaches to a drill and it solved my slow drain problem.

 

[Music Lover]

My guess is it needs snaking. I bought one that attaches to a drill and it solved my slow drain problem.

That could be it but before trying anything else I'd first loosen the fitting and raise up the drain line so that it slopes downhill. That would take 30 seconds.

 

[NW-Bound]

The vent for your tub is the handle or flipper to drain the tub. It is the one with one or two screws...

The tub I have in the bathroom upstairs is like that. It is actually the overflow outlet to keep the tub from getting overfilled. The overflow channel allows air above the J trap to escape.

The tub I was describing with the problem caused by the strainer is in my master bathroom. It does not have an overflow outlet.

Glad you brought this up, because I did not describe the whole situation.

Similarly, most bathroom sinks have an overflow outlet, and this also serves as an air vent. The OP sink does not have an overflow outlet.

The wash tub in my laundry room installed next to the washing machine also does not have an overflow outlet. And I believe it is the same situation that Jerry described with his wash tub, which was helped by a manual swirling action when drained.

 

[Winemaker]

The tub I have in the bathroom upstairs is like that. It is actually the overflow outlet to keep the tub from getting overfilled. The overflow channel allows air to escape.

The tub I was describing with the problem caused by the strainer is in my master bathroom. It does not have an overflow outlet.

Glad you brought this up, because I did not describe the whole situation.

Similarly, most bathroom sinks have an overflow outlet, and this also serves as an air vent. The OP sink does not have an overflow outlet.

The wash tub in my laundry room installed next to the washing machine also does not have an overflow outlet. And I believe it is the same situation that Jerry described with his wash tub, which was helped by a manual swirling action when drained.

You should have some kind of access door behind or below the drain/diverters. This should allow you to view how the drain is vented.

I really believe that the OP has very tight spring on their under sink vent, which is not allowing to drain all the time. Also, water weighs 8.34 #/gallon; OP states that it doesn't drain well with slow flow, so the vertical stand pipe must fill to a point where the weight of the water must be able to push the water out of the trap. That would make me ask the question as to whether the sink drain pipes are 1.25 or 1.5". Most bathrooms are 1.25", the smaller drain pipe would allow the water to move faster. The pitch of the drain pipe is immaterial, unless it is over a very long span, which the picture shows it is not.

 

[NW-Bound]

You should have some kind of access door behind or below the drain/diverters. This should allow you to view how the drain is vented.

My bathtub sits at ground level and on a concrete slab. There's nothing between it and the underground J trap.

My wash tub is like the following photo. There's nothing to inspect between the tub and its J trap mounted immediately underneath.

 

[ERD50]

... I really believe that the OP has very tight spring on their under sink vent, which is not allowing to drain all the time. ... The pitch of the drain pipe is immaterial, unless it is over a very long span, which the picture shows it is not.

I don't agree with this. As I said earlier, the only purpose of a vent stack (or air admittance valve/vent), is to prevent the suction from other drains sucking the water out of the trap on this sink. It has no bearing on the draining function. Think about a big picnic water cooler with a tap on it. It just drains. The air is replaced above, just like the open sink basin. Neither one needs a vent.

As NW-Bound has been saying (I'm also too lazy for a picture), if there is a blockage, or just small holes/screen in the drain, between the basin and the trap, air might get trapped in that space, due to surface tension of the water. A full basin will overcome that.

... The pitch of the drain pipe is immaterial, unless it is over a very long span, which the picture shows it is not.

I do agree with this. It's still all below the basin, it's not a problem for draining. Over the long term, that can build up crud and cause a blockage, but OP has had it apart and cleaned it, so that's not the issue.

-ERD50

 

[Sunset]

.....

...... Probably should have snaked the piping within the wall when I had the drain piping off, but I didn't. Besides, the only snake I have is really for fishing wires though walls and not cleaning piping.

......

A fishing wire isn't a plumbing snake.
This is the type of snake I use when things are really clogged up.
It's not for use on a toilet, but works on all other drains.
Get the one that is 25 feet long, and can be optionally powered by a drill.
I've only turned mine by hand the 2 times I've used it.
It cannot hurt to make sure the pipes are clear.
Many available for ~$25

 

[ERD50]

A fishing wire isn't a plumbing snake.
This is the type of snake I use when things are really clogged up.
It's not for use on a toilet, but works on all other drains.
Get the one that is 25 feet long, and can be optionally powered by a drill.
I've only turned mine by hand the 2 times I've used it.
It cannot hurt to make sure the pipes are clear.
Many available for ~$25

it can't hurt, but it doesn't explain this from OP:

However, if the basis (basin?) is allowed to reach a higher level (say 3 inches) then the basin seems to overcome some pressure restriction and always drained very quickly (few seconds).

Unless the clog is acting like a flapper, opening and closing with pressure, which is very hard to imagine, and would not have that effect past the trap anyhow.

-ERD50

 

[Music Lover]

I do agree with this. It's still all below the basin, it's not a problem for draining. Over the long term, that can build up crud and cause a blockage, but OP has had it apart and cleaned it, so that's not the issue.

-ERD50

But the problem was draining when there was very little water in the sink. Theoretically, it's possible that the amount of water in the sink in those instances isn't enough to exceed the weight of water in the part of the drain line that appears to slope the wrong way. So it sits there or drains very slowly.

When there's more water in the sink the weight of it ensures that gravity takes over. It's basic physics.

All they have to do is loosen the fitting and raise the drain so that it's level or has a slope in the right direction. That takes 30 seconds and could immediately solve the problem.

Why do anything else before trying that?

 

[Winemaker]

My bathtub sits at ground level and on a concrete slab. There's nothing between it and the underground J trap.

My wash tub is like the following photo. There's nothing to inspect between the tub and its J trap mounted immediately underneath.

I may have misunderstood your description.

Yes, like Jerry and you have said the "normal" volume of water in a wash/laundry tub creates a whirlpool that allows for water to go down an unvented sink. Your unvented bathtub may be plumbed the same way but I thought you may have had a hidden vent in an access door. I'm sure the tub is vented through the roof.

 

[NW-Bound]

I may have misunderstood your description.

Yes, like Jerry and you have said the "normal" volume of water in a wash/laundry tub creates a whirlpool that allows for water to go down an unvented sink. Your unvented bathtub may be plumbed the same way but I thought you may have had a hidden vent in an access door. I'm sure the tub is vented through the roof.

Yes. Everything is vented, after the J traps that is.

My bathtub shares the same vent as the two bathroom sinks and the toilet. The others don't have the problem with draining, nor does my bathtub if I just lift up the strainer temporarily to let the air before the J trap escape. The air after the J trap is of course already vented by the plumbing built into the wall.

Again, this particular bathtub does not have an overflow channel, which would serve as an air vent prior to its J trap.

Similarly, my laundry tub shares the same inwall vent with the adjacent washing machine. The washing machine has no problem with draining, because its outlet hose just drops into the standing pipe in the wall. The loose fitting of the washing machine hose allows air above the associated J trap to escape. Else, you would need pressure to push all that air past the J trap.

PS. Because of the washing machine discharge hose just drops into the inwall standpipe, any clog downstream would cause a major flood!

 

[ERD50]

But the problem was draining when there was very little water in the sink. Theoretically, it's possible that the amount of water in the sink in those instances isn't enough to exceed the weight of water in the part of the drain line that appears to slope the wrong way. So it sits there or drains very slowly.

When there's more water in the sink the weight of it ensures that gravity takes over. It's basic physics.

All they have to do is loosen the fitting and raise the drain so that it's level or has a slope in the right direction. That takes 30 seconds and could immediately solve the problem.

Why do anything else before trying that?

Sure, they could try it. But the bottom of the sink basin looks to be a good 6" at least above the horizontal drain pipe. So if the slope added, say, 1/2", water is going to drop. Either 6" or 5 1/2" would make no real difference. It's not until that drain got very close to the bottom of the basin that it would have an effect (or affect? I give up! ).

-ERD50.

 

[NW-Bound]

Looking again at the photos posted by the OP, one way to check out my theory before he dismantles and throws away the existing sink is this.

Drill a hole in the tail pipe below the sink, but above the J trap waterline. Use RTV or epoxy to fasten a plastic tube to serve as an air vent. The next problem of course is how to run this tubing so that its end is higher to prevent water from spilling. Also, the run of the tube has to be sloped such that it will not have standing water. Else, this makeshift vent will have its own J trap.

The above arrangement will have the same effect as the usual bathroom sinks, which all have their own vent via the built-in overflow channel.

Again, the needed vent here is the one before the J trap, not the one after the J trap.

 

[Music Lover]

Sure, they could try it. But the bottom of the sink basin looks to be a good 6" at least above the horizontal drain pipe. So if the slope added, say, 1/2", water is going to drop. Either 6" or 5 1/2" would make no real difference. It's not until that drain got very close to the bottom of the basin that it would have an effect (or affect? I give up! ).

-ERD50.

I agree. But we only see the drain line until enters the wall. Maybe it runs horizontally or even slightly uphill for several feet before going down?

 

[NW-Bound]

Sure, they could try it. But the bottom of the sink basin looks to be a good 6" at least above the horizontal drain pipe. So if the slope added, say, 1/2", water is going to drop. Either 6" or 5 1/2" would make no real difference. It's not until that drain got very close to the bottom of the basin that it would have an effect (or affect? I give up! ).

-ERD50.

+1

When there's only 1/4" of water in the sink, that water has to percolate through the holes in the strainer.

If the trapped air below the strainer (but before the J trap) is vented, that little head of water will have no problem dropping right through.