Help: ABS to Cast Iron Fernco Hub Donut (rubber) Leaks

[ejlindahl]

It took 9 hours of carefully drilling, chiseling and prying loose three lead & oakum cast iron hub joints in a very tight work space. I had to use mirrors on 2 of the wyes as they were facing the concrete wall with only a few inches of clearance. I am proud I got em all with out busting the hubs and only 2 broken drill bits.

I was ready to redo the galvanized drain that led into those cast iron hubs with ABS. I got 3 Ace Hardware "Compression Joint Sealer" rubber donuts, (generically known here as Fernco hubs) slapped them into the wye hubs and hammered in some ABS and glued up the rest of the run. Filled it all up with H20 and water comes dribbling out all three of those rubber donuts. More than a dribble! Maybe a cup a minute per hub! And this was with only 2' of head pressure (~1psi) because I only filled the stack up to the level of the toilet flange on the floor above. The runs were overhead just below the basement ceiling.

In my prep, after ensuring all the oakum and lead were out of the hubs I used a ~2.5" diameter wire wheel in my drill to really clean up the inside of the hubs. They were burnished smooth and clean. However, the inside of the hub was not even and fair as you would see inside an ABS hub for gluing. Instead the inside of the cast iron hubs were slightly scalloped and minimally pitted with low and high places varying I'd guess about a 1/16 of an inch or so. But there were no abrupt transitions that I could see, such as a casting transition lip/step or deep pitting. I figured this unevenness was normal in 75 year old CAST iron pipe. None of these joints had ever leaked but the inside of the hub did appear to have some evidence of rust discoloration (not rust scale), and minimal pitting, but this may just be the way they look inside after sand casting, if thats how they are manufactured. Also I used vaseline to lube and hopefully help seal the donuts into the cast iron hub.

My question is why are these leaking?? The donuts were a snug fit, taking a bit of force to get into the hub. There were 4 concentric rings molded around the rubber donut to aid in the seal. And when I put in the ABS stubs I had to hammer them in even thought they were throughly slathered, inside and out, with vaseline.

The leaking will only be a problem if the sewer line gets plugged and there is a sewage backup up to the level of these joints (six feet above the basement floor). Otherwise, under normal circumstances, gravity and the male/female aspect of these near vertical (45 degree) wye hub joints will have the lav and tub waste flowing merrily on its way

I am loathe to mess with oakum and lead wool as the clearance around 2 of the hubs is so tight. I could suck it up and do that though. Also I thought; maybe I could use silicone or acrylic latex painters caulk or even a high end marine sealant instead of vaseline. All those are slimy so would lube the fittings when I put them together then they would set up and do a good job of sealing the joint.

I am inclined to go the caulk/sealant route. What to you all think?

Of course this means I have to cut the ABS, yank out the stub from the donut, pry out the donut from the hub and scrub all the vaseline off. Then get a few new ABS fittings and no hub connectors and slap it all back together, wait for a few days for the sealant to dry/set and retest with crossed fingers.

I would appreciate any advice on my options or if you have another option:

1. Leave it be and it will be just fine unless the sewer line backs up. It never has in 25 years.

2. Go the caulk/sealant route. But I wonder how careful I have to be of chemical compatibility with the rubber donut. I think this would work just fine with the acrylic painters caulk. I'll probably go this route.

3. Go the oakum and lead wool route. You will really have to talk me into doing this.

Thank you for your advice.

Eric

 

[frodo]

those are a triple pain in the ass to deal with.

you should be useing a gasket called Ex tight by tyler

they have 4 ribs,,,,the biggest problem is that abs/pvc and cast iron are NOT the same OD

so pushing the pipe into the gasket is very difficult. usually

very often,,,most of the time

the leak you are talking about is because your pipe is in the hub

up to the 4th rib.

pull the pipe out.

go buy some BLACK SWAN and then, file the end of your pipe

round the end
fold some duct tape on the pipe use bkl swan push it home while twisting

 

[ejlindahl]

Thanks for the reply Frodo.

Does the Black Swan have some body or thickness like caulking does? I ask because I think the leak is caused by the uneven scalloped nature (inconsistent diameter???) of the inside of the cast iron hub and the ribs on my rubber donut are not big enough or maybe pliable enough to fill the void of those scallops. Caulking has the body or thickness to fill and seal those voids. Will Black Swan do this??

I did carefully and fully taper and round and smooth the tip of the ABS pipe I inserted into the donut. And it did require a hammer to insert even with vaseline slathered all over. But it only needed moderately firm hits with my 16 ounce framing hammer. A 15 pound hammer would have been overkill, (thats really a pretty heavy sledge hammer!!!). Should it really be that tight that you need a 15 lbs hammer?

Tyler Pipe website lists the product as EZ-tight. My search did not reveal that they had something called X-Tight so I'm sure this is what you mean as the EZ-Tight looks like the donut I bought from Ace Hardware, same size and number of concentric rings, etc.... I believe in quality products and everything but this is not that technical and I don't see how the Ace donut would be effectively any different than the Tyler. By the looks the Ace could even be made by Tyler in this day and age of globalization. If the Ace donut is tight enough to require good blows with a hammer I would think that it would be tight enough to do the job. I think your solution of black swan is the ticket or maybe a quality, thick caulking.

When you say the "problem is that my pipe is up to the 4th rib" do you mean that it's only inserted a little, ie just into the 1st rib, which would be the 4th rib away from the bottom of the cast iron hub? I marked the pipe before insertion and it is definitely bottomed out at the end of the donut, ie inserted at least 3 inches into the hub. It is 1.5" ABS into a 2" cast iron hub so I had to mark it to be careful not to insert it too far so as not to intrude into (and obstruct) the vertical part of the 4" stack. That is why I marked it to get the proper insertion amount.

The duct tape is a mystery to me. By saying fold it over do you mean that it is folded over the end of the ABS pipe so that part of it is stuck to the inside diameter of the pipe? What is its purpose? Won't it eventually unstick and be a little flag inside the drain pipe. Probably wouldn't cause an obstruction but I don't get it's purpose. Or is the purpose of the tape to smooth the tip of the pipe so it doesn't snag on the rubber donut? My pipe was carefully tapered and smoothed. Could you explain the purpose of the tape a little bit more and exactly where its applied?

So:

Does Black Swan have the thickness to fill the scalloped voids within the hub/donut interface?

What is the purpose and exact location of the tape?

Isn't 5 or 10 good moderate blows with a framing hammer indication that my Ace donut is tight enough?

Thanks again for helping me out. I appreciate you time.

Eric

 

[frodo]

caulking is for covering nail heads before you paint

it is not for plumbing...the sealer i mentioned is what is required.


most likely,,,your pipe is not all the way in.

measure the hub depth, mark the side of the pipe

did you use any lubricant at all ?

soap ? or did you dry ---- it ?

if you bevel the end, wrap tape around it,fold he tape over,,,lube it

it goes in easier...

to answer your question about the thickness of black swan

the ****s like tar,,,,thick, nasty, black ****, that gets on everything

you put it together with ....I GUARANTEE it wont leak

the purpose of the tape is to make the end smooth so it will slip by the ribs.


how many times you hit it with a hammer means nothing.

plastic pipe is NOTORIOUS for hanging up on the last rib.

I my self have spent 30 minutes beating the hell out of a 2x4 on top of a pipe with a 10 lb sledge

MArK THE PIPE

bottom line....if the pipe is not all the way in, it will leak,,no matter what sealer you use.

as i have said before...the end of the pipe,,is hanging up on the ribs

bevel and tape the pipe..if it still wont go,,,you may have to shave/sand off a couple thousands off of the pipe

as i posted earlier, abs has a larger OD than cast

 

[ejlindahl]

Good to hear that Black Swan is "like tar". So it has some thickness and will fill the small void irregularities in the cast iron hub. I'll get some and use it.

Ending with fine sandpaper I tapered the ABS as smooth as any supository (see picture of a slice of ABS I messed up on) and slathered it in vaseline, (no personal experience with this though). I'll pull it out of the hub, clean it up, slather it with Black Swan and mark it to be sure I hammer it all the way in (past the last donut rib).

I think I understand the purpose of the duct tape; it is just to give the "point" of the ABS taper a little more slickness and/or taper to get past all the ribs on the rubber donut. See picture; from your diagram above this is how I envision the tape should go on the end of the ABS pipe. Is this correct or should the duct tape only slightly fold over the end as is shown in the 2nd picture. With the longer fold over part it will end up with a little "flag" of tape that the drain water will have to pass by, (not a big problem that I can see). Note the marks I made on the pipe to guage how far into the hub the pipe is inserted.

BTW the old drain pipe that was leaded into the cast iron wye on the stack was galvanized steel, not cast iron.

Thank you very much for your advice.

 

[frodo]

the duct tape will rot and go away with time...

push and turn while you wiggle it back and forth.. good luck

 

[ejlindahl]

Thank you Frodo,

I figured the tape would rot and go away, too. Now I'll call the pro plumbing shop to see if they have that Black Swan.

 

[ejlindahl]

So I talked to the local pro plumbing shop and they said they don't recommend, nor do they use any lube/adhesive with these rubber donut ABS to CI hub connections. Sheesh. I need something so I'm gonna buy the Black Swan stuff online ………. at $25 + shipping.

 

[Mr_David]

the duct tape will rot and go away with time...

push and turn while you wiggle it back and forth.. good luck

Curious. What purpose does the duct tape have? ABS pipe has a slightly larger diameter than the cast iron soil pipe.

 

[ejlindahl]

Mr David my take is in post #5 above and Frodo seemed to confirm this:

"Frodo, I think I understand the purpose of the duct tape; it is just to give the "point" of the ABS taper a little more slickness and/or taper to get past all the ribs inside the rubber donut. See picture; from your diagram above this is how I envision the tape should go on the end of the ABS pipe. Is this correct or should the duct tape only slightly fold over the end as is shown in the 2nd picture. With the longer fold over part it will end up with a little "flag" of tape that the drain water will have to pass by, (not a big problem that I can see). Note the marks I made on the pipe to guage how far into the hub the pipe is inserted."

 

[frodo]

it is an old trick for getting stubborn pipe to ease into the gasket.

past the last rib