View Full Version : Fixing bathtub drain leak

02-10-2011, 09:13 AM
Hi there,

I have a bathtub drain leak I want to fix (see picture)


I wonder if I should

- use plumber's putty and apply to the underside of the flange on the new tub basket, OR
- use a rubber tub drain gasket instead of plumber's putty
- silicon caulking

This is a cast iron tub. I wonder which one lasts longer -- and easy to fix/replace if leak occurs again in the future.


02-10-2011, 09:54 AM
Haven't done this before--

I wonder, is there supposed to be a gasket between the tub shoe and the bottom of the tub? As the picture shows, there is no gasket there visible from under the tub.

Do I drop the gasket in from above after I remove the drain flange, or I need to remove the tub shoe from under and slide it in under the tub and then reinstall the tub shoe?

Also, do I need to ensure where the rubber gasket meets the bottom surface of the tub and the top of the tub shoe are smooth (use sand paper to sand it down if there's rust?)?

And, would I need to apply silicone sealant to the top/bottom of the rubber gasket?


02-10-2011, 10:28 AM
You are going to have trouble with the rust. I would: coat a new gasket with silicone. After setting that and wiping off excess silicone, I would coat the entire area with Henry's 208. I will deny that I ever said that, but it will last at least as long as that tub is liable to last.

02-10-2011, 11:02 AM
I wonder how to install the gasket:

Do I need to remove the overflow pipe first?

Right now, I can see the tub shoe is not @ 90 to the overflow pipe. It is tilted downward as it touches the tub bottom. I would need to readjust the overflow pipe's length if I were to install the gasket from under the tub?


02-10-2011, 11:32 AM
You can unthread from the top, and then slip the rubber gasket between the tub and the brass. Silicone sounds like a good idea with something that old.
If it were all new, then it wouldn't be needed.

Since this is all open, it might make sense to replace the overflow drain at this point.

02-10-2011, 12:42 PM
Thx. I need to go under in the crawl space if I replace the overflow drain... .

I wonder if I am to replace the overflow drain set, a brass set is superior compared to white PVC/black ABS-true? I heard PVC/ABS causes drain noise (or it won't matter since it's a very short length?).

What'd be a good brass set someone can recommend?

Also, do I use silicone sealant, or silicone caulking?

02-10-2011, 12:45 PM
We mainly replace using solvent weld ABS drains now.
The brass with slip joint can leak.
Noise? It's just a drain. But yes, ABS or PVC in the wall do make noise as the water drains. Not on the tub drain though.
Cast iron pipes are pretty quiet. I've done commerical buildings with those, but not homes.
Steve Balmer has cast in his home.

02-10-2011, 03:13 PM
Just wonder between ABS/PVC which type works better for like CA, where there are occasional smallquakes in the year. Would PVC still leak since it's not like ABS where it's solvent welded, or if it's tight enough PVC should still hold good?

Thx... .

02-10-2011, 05:13 PM
PVC and ABS are both solvent welded, they just use different solvents for each.

02-10-2011, 06:05 PM
It looks from the staining like it is leaking down from the overflow as well.

02-11-2011, 12:58 AM
I tried slipping a rubber gasket in and tighten up the drain flange just to see how well that worked. Water leaked thru' the gasket as the rubber gasket caused the tub shoe to tilt downward further, so one side of the gasket was really tight while the other side still showed a bit loose. I did not put in silicone sealant as that was just a test. As I moved the tub shoe around a bit, that caused the lower end of the overflow pipe to start leaking.

I've now got a Watts PVC tub drain:


Like other PVC piping used indoor under the sink, you'd turn a slip nut to tighten up the connection.

I wonder if this PVC kit would suffer the same potential leak problem as the brass tub drain kit, since in both kits a slip nut is used in the connection of two pipe sections.

Is there another PVC drain kit that is meant for welding?

02-11-2011, 06:36 AM
We don't get our supplies on amazon or the bay.. Go into any hardware store and they will have all the various types of drains lined up on one shelf.

If we have the "big one" in CA, the least of your worries is the tub drain. Otherwise, no worries mate. In many places, either PVC, or ABS, but not BOTH, will be the local material of choice. Not because one is better, but suppliers often just develop a local preference, no particular reason. In the Southern Calif. area it is ABS, you don't find PVC much. I don't know about LA county. That doesn't really count as S. Calif. It is just lala land!

02-11-2011, 07:26 AM
There are some tub drains that have some designed in 'give' to ensure the overflow and drain shoe can seal without undue stress on the connections. Often, on those that don't, one or both of the seals are beveled to account for the overflow not being exactly perpendicular to the drain shoe, and on those, you must ensure you get the bevel the proper orientation to get a good seal.

09-08-2011, 02:22 PM
Been delayed for a good while. I finally get the time now to replace the bath drain. I am going to use Schedule 40 plastic and glue so no need for slip joints.

I wonder in connecting the 1 1/2" Schedule 40 plastic tailpiece to the 1 1/2" threaded galvanized pipe (see the vertical pipe piece in lower left in the above picture), do I need to use a Fernco shielded coupling for the transition since the Schedule 40 plastic is too thick to fit into the galvanized pipe, or there's anything better?

09-08-2011, 08:51 PM
I would replace the tub drain (waste and overflow). If you have it open and accesible doesn't make sense ti just replace a gasket. Clean the drain hole very good and set the new shoe with silicone. Gererit drains are very good as you will never have any issues with the pop up.

09-09-2011, 01:55 AM
Two things I'm running into now:

1. Slanted joint

I just realize that when I change from brass drain pipes to Schedule 40 drain pipes, the positions don't match up to the original galvanized piece coming up from the main cast iron drain pipe. This is because the Schedule 40 pipes are thicker than the brass pipes, and so positions don't align right anymore.

So either I would try to glue the plastics to the Tee at a slightly slanted angle, or I'd need to try to move the cast iron pipe's position--which I'm not sure if it's possible--since that's such an old iron pipe and the threads might all be frozen now.

Would it be ok if I glue a Schedule 40 pipe to a Tee but it's a bit slanted and not straight at the joint. Would there be possibly leak later on even if I put in enough cement for that slightly slanted joint?

2. The old brass drain pipe's overflow gasket was flat. Perhaps it was 'flattened' during the install of the brass drain pipe to align with the main drain pipe's position.

Now that I'm installing a new drain, the new overflow gasket is fatter on the bottom.

If I were to install the new overflow gasket correctly, it'd further tilt the vertical overflow drain pipe away from the tub at the lower end, causing further misalignment with the cast iron drain pipe below.

Should I try to press on the new overflow gasket (i.e., flattening it) so it'd align with the cast iron drain pipe's position correctly then? Would the flattened overflow gasket cause leakage at the overflow drain later?

Or there could be another solution to this?

(BTW, the overflow elbow is slightly slanted already.)


09-10-2011, 01:41 PM
It seems this mismatching of the new drain pipe location to the cast iron pipe's location could be potentially a hack of trouble for me.

I was talking to someone in *********. The guy was a plumber before.

He mentioned that if the joints on the Schedule 40 tee aren't done 100% straight (slanted slightly), there will be leaks later on even if I glue them all tight.

He said that I'd need to move the cast iron pipe to 100% match up w/ the tub drain pipe so everything is lined up 100% straight. That way I won't need to glue the joints on the tee slightly slanted that would cause leaks later on.

Anyone can confirm what he said about the potential leaks from the slightly slanted plastic joints on the tee?

Thx... .

09-10-2011, 02:17 PM
The overflow washer can be spun if needed, depending on the slope of the tub. There is no rule that says it can only be one way.

With a glue on W&O, I sometimes installed to end fittings, overflow and shoe, and then glue the tee with sections of pipe to those. The p-trap is the last thing I do.

However, that is not always possible.
In that case, you sometimes build it up from the bottom.

09-10-2011, 07:04 PM
Thx for the suggestion. I'm a bit relieved now. I was having lunch a bit earlier and bumped into someone who did commercial mechanical jobs and he suggested that there were other ways to make it work w/o moving the cast iron pipe:

- don't touch the good old cast iron pipe if it's all frozen and hard to move it--it's too old and attempts to change it might break it...
- For the overflow elbow, instead of using the bevel gasket, get a flat rubber piece and cut into a gasket myself. That way it's less offset to the cast iron pipe (how come I can't find a flat gasket for the overflow elbow?).
- Slightly off-angle when joining the pipe sections to the tee is still ok. Cut the pipe end a bit off-angle to compensate so when pushed into the joint the end fits snugly.

BTW, this is how the piping looks right now (off-angle). You can see the piping is slanted to the left.


(the pipe sections aren't glued to the tee yet)

I'll try to find a flat piece of gasket or cut a piece from a flat rubber to help out a bit... .

09-10-2011, 10:34 PM
I notice that there's a very very slight leak from the male threaded galvanized pipe end thru' the lower-end of the Fernco Proflex coupling (CP-150, for 1-1/2" CI, PL. or ST. to 1-1/2" PL. ST. or XHCI). I believe I've tightened the screws on the coupling pretty well.

Is the water leaking from the lower end of the Fernco Proflex coupling because it's a male threaded galvanized pipe end I'm inserting into the coupling? Should I try something else?

(The short PVC end from the drain tee doesn't allow me to use a galvanized coupling for a male galvanized to male PVC connection.)

Someone mentioned "No Hub" coupling. Wonder what the difference would be?

09-15-2011, 01:34 AM
OK, I've finally installed and glued the pieces to the tee.

The next thing I've found out--the plunger did not help hold the water in the tub, so water leaked out even when the trip lever went up (which dropped the plunger down to block the water).

This is just a simple plastic plunger--no gaskets, no O-rings around it.

I added some weight (some nuts and large washers) just to see if it'd help. The added weight helped a bit, but there was still a gradual leak.

BTW, this is a Keeney model 640PVC bath drain.



What can I do to help the plunger block the water better so there'd be no leak?

1. Add silicone grease?
But even if it works, the grease would eventually wear out and I'd have to reapply the grease again--true?

2. I thought about coating a layer of silicone sealant around the base of the plunger--to help seal off the contacting points.

Would this help? And, would this only work temporarily--since the silicone grease would still wear out and peel off overtime?

Any other ideas/sealant that can help? Or trip lever - plunger type stopper just doesn't work reliably at all with plastic material?

09-15-2011, 09:48 AM
It's a much easier installation if you replace the p-trap at the same time.

09-15-2011, 11:19 AM
Sorry if I miss this,

don't know if it's suggested that fixing the p-trap would help w/ the trip lever mechanism?

Right now the only thing is the trip lever/plunger mechanism isn't holding the water from a leak when the lever is in the up position. Everything else is working now.

Don't know if anyone has tried the Keeney Schedule 40 drain set (trip lever) and would know how to get that plunger working right... .

09-15-2011, 12:00 PM
If the tub drain and parts are new, then the adjustment should make it hold water.
The bucket may not be dropping far enough down to seal.

If you have it all assembled with the old trap that is fine, I was just pointing out for others that cutting the trap out is an easier method. I also prefer a new trap anyway.
If you have it working, don't worry. You're done.

09-15-2011, 02:59 PM
Thx. Now that I see your comments, I look and notice that the off-angle I mentioned earlier was actually introduced by the old p-trap not going straight up.

Would have had replaced the p-trap and set a new one straight up and taken care of the off-angle issue I struggled with earlier had I seen your comment at an earlier time. :-)

Though, not sure if the installation of that old p-trap was done purposely a bit off-angle to provide a slight tilt for the tub drain to drain water faster?


BTW, I fiddled quite a bit w/ the trip lever/plunger not holding water's problem.

I removed the face plate, and completely dropped the plunger into the tee so to remove the linkage length relationship altogether--and it was still not holding water when the plunger was completely down at the bottom of the tee.

Then I applied by hand some pressure to the plunger by pushing the linkage down further. I sensed that the plunger didn't go down any further, but the water held -- only as I gave more pressure.

So I wondered if the plunger didn't fit well 100% with the tee's hole, therefore allowing a very slight gap where the plunger met the bottom of the tee--and hence a leak.

I noticed the lever on the face plate has a spring and could provide some modest pressure, so I purposely set up the linkage just a bit longer than needed, so when the lever was up (and pushed down the linkage and plunger), it gave the plunger a slight constant downward pressure when the plunger was already completely down in the tee.

The additional slight downward pressure with this 'trick' seemed to help provide a better hold of water.

I don't think it's meant to use the additional pressure from the spring in the face plate to get a good seal of the plunger down in the tee to hold the water.... . This is just a trick I seem to get the plunger to hold water better... .

It's quite tricky to do this right. The linkage cannot be too long (perhaps just 1/16 inch longer than needed), or the wire sections would turn further and the total length would reduce again, removing the pressure to the plunger--and the water would start leaking again thru' the plunger.

Perhaps the manufacturer could fix this defect so folks won't need trick like this to make it work properly... .

If anyone else has a better idea to help the plunger hold water better I'm completely open... .

I called the manufacturer (Keeney) and they said that the plunger is supposed to still *leak* water slightly even when it is working properly to hold water (true?)

Also, I wonder if the slight off-angle of the tub drain would cause the plunger to not seat properly in the tee since the tee is not 100% straight up but slightly off-angle?

09-15-2011, 08:52 PM
I think I'd put a good layer of silicon plumber's grease on the plunger and see if that helps. If the thing was a perfect fit and held water without it, as it got the hot water flowing through it, it might expand enough so you couldn't move it.

09-19-2011, 03:17 PM
Thx. I'll try the plumber's grease--although my guess is the grease would wear out in time though?

Both the tee and the plunger would expand on higher temperature, so I wonder if the plunger would get tighter, or more room in the tee, or no change?

> Also, I wonder if the slight off-angle of the tub drain would cause the plunger to not seat properly in the tee since the tee is not 100% straight up but slightly off-angle?

I figured out myself that the plunger is 100% inside the tee when it does down completely. If the hole in the tee matches up the plunger's shape completely, the slightly off-angle of the drain should not cause any concern (leaks).