I'm making a transition from Cast Iron to PVC underground and have tried 2 couplings both with very small leaks. The first was a shielded 2 band coupling from Home Depot. After some digging, I saw that this was a little smaller than the heavy duty couplings the Pros get. So I bought a Mission 4 band Heavy Duty coupling [www.missionrubber.com]. I also re cut the Cast to ensure I had a straight cut and lined everything up and tightened to exactly 80 lbs an inch. Still have a leak.

Part of the problem I feel is that the water will pool at the transition. The cast has 30 years of crud on the bottom which makes a 1/2" flat bed on the bottom. I think maybe the water comes down the PVC and pools there since it has to work it's way over that corroded bottom. I removed the coupling, cleaned down the pipe a bit, but still have the leak. I also think possibly a problem is that I have the PVC sloped slightly coming into the Cast, so this maybe causing a sort of bind at the bottom of the coupling (maybe?). I could offset this a bit by cutting the pvc with a slight bevel, but that doesn't seem right.

I'm running out of ideas. I've searched the threads and read that some use Silicone on the cast side to seal the rough cast. I haven't tried this, and was wonding if a seal of plumbers putty would do the trick. The cast iron is very rough and I've used a steel grinder on a drill, but it didn't do a whole lot.

I've also read that maybe this mission coupling isn't the best since the pipe isn't truly meant for a no hub, and perhaps the CP44 will work better. [www.missionrubber.com]

I bought it and will have it in a few days, but am not 100% confident it will be perfect. I have just about every coupling they make for this transition now...ha ha.

I was hoping some of you could give me some insight on the best fix. I'm going from old rough cast to new pvc. I want it to be leak free before I cover it and finish my lines. Thanks in advance!!

Get a quality transition band from a plumbing supply house...the right CI to Pl shielded band. Use a grinder with grinding wheel to clean up the CI pipe. If needed cut the CI pipe square with a grinder and cutting wheel. Use eye protection of course. Leave 1/4" space in between existing CI and new PVC. Tighten bands to correct torque. //post pic for better advice.

Doug,
Are the mission bands not quality? That was what was recommended most often.

Mission Band is fine.

Using silicone will fill any voids in the rough surface of the cast and create a seal. Just torque down the bands as normal. If you can find Lexel silicon, it is probably the toughest and stickiest silicone you can find. It is as sticky as a toddler eating candy.

When clamping to rough cast iron, I find that a little bit of silicon will make a water tight seal.

Thanks for the suggestions! I figured people used a little bit of something to make the seal tighter. The old cast iron is very rough. I may try to smooth out obvious protrusions with cutting wheel.

Something tells me that silicone is going to get really messy as those gaskets are tight fits.

So, I'm between two connectors. I have a MIssion C 400 HW currently on there [www.missionrubber.com]

HOWEVER, it seems that is made more for no hub pipe, which I'm thinking in 1940 when my house was built, didn't exist. SO, I have a Band Seal P400 which is designed for XH CI to Plastic on they way. Is the the P400 is the coupling I should be using? The leaded hubs on the cast confirm XH.
[www.missionrubber.com]

I'll probably try using the P400 without silicone first. See if that leaks, then if so, I'll put a thick messy silicone layer on the cast and fit the coupling.

I'll try to post some pictures. If for nothing more than to show the difference in couplings. The Mission weight coupling is night and day on the quality, size, hardware, etc. when compared to the one from the box store.

Not a plumber but I have also done about a dozen or so transition from old CI to new PVC at my house and never had a problem with leaks.

Having said that when I last did it a few years ago Fernco makes a PROFLEX shielded coupling that transitions from CI to PVC and you can tell the rubber sleeves the thickness is just slightly thicker on the CI side. Recently I noticed they no longer make a special same size transition coupling for CI to PL, they just have one that goes from same size CI/PL to CI/PL so I guess the slight difference is not significant enough for it anymore.

I have also used a PVC no hub adapter a few times. This is a special fitting that is glued to the PVC side to make it more suitable for a no-hub coupling:

[www.nibco.com]

I have used that a few times to connect to CI with a standard no hub coupling because I think it "lessens" the outer diameter of the PVC to be more equal to that of the same size CI. Not sure it made a real difference though.

I wouldn't worry about how messy the silicone is on an underground installation- it will seal up tight. How much messier is silicone than playing in a hole filled with mud?

rather than silicone, i would use permatex form-a-gasket.

what benefit would you have between a drying and non-drying compound when the rubber of the coupling would simply crack regardless if you try to remove it anytime after 2 years?

Fernco's Proflex web page shows the 3000 series couplings for CI to plastic, steel or XH CI, while the 3005 series is for plastic, steel or XH CI to plastic, steel or XH CI.

Something I just saw on that web page in bold type, is a maximum test pressure of 4.3 psi.

What if you have over 10' of head piping?

then you test with air pressure to 4.2 PSI..

When would you be pressure testing an 50+ year old drain system?

Hah... I wish the messy hole was just mud.

I'm going to try the current mission coupling another time tonight when I get home. The "leak" is just a few drips, so it's annoying that this is holding up the rest of the project until I figure it out. Overnight, it accumulated about a half a cup of water. I placed some plastic sheeting under the transition to see how much it was leaking. Nevertheless, I'm not satisfied until it's dry.

A few days past and I have some theories why I'm struggling with that connection. I'll try some things and report back. If I can't get it without, I'll silicone the cast and move on. I'll try and post some pictures tonight.

Thanks again for all the responses.



Edited 1 times.

I would guess that the bottom of the cast may have a pinhole close to the coupler and not under the rubber.

possibly. but he said he tried the four banded version and the four banded ones have longer sleeves and torque to 80#, so if the hole is close to the edge the four banded sleeve should have covered it?

No luck here in Plumbville. Still have a pesky leak at the location, although it is very very slow at this point, it's still there. Had maybe 4-5 drops in 6 hours. Hardly noticeable, but still there. I haven't added silicone yet, so that would likely fix any tiny drips.

HOWEVER, I took the coupling off and to my surprise, about half a gallon of water poured out with some stool. This is a surprise because the only line that drains into this cast is the kitchen sink, no toilet.
There used to be a toilet attached, but I removed that section of cast and haven't plumbed that PVC section yet until this coupling is right.

I removed all the PVC, checked the slope of the existing cast, and it is just over 1/4" per foot headed to the main stack.
Can anyone answer why some stool be coming out of this section of pipe? It seems pretty recent since there was some small tissue bits. There hasn't been a toilet attached for a few months, so I guess it "could" be remains, but seems like a lot of water coming from this section of cast. This also happened when I just capped the cast pipe before running any plumbing to it. When I removed the cap there was quite a bit of water waiting there to drain.

The kitchen sink is a LONG run of PVC. It vents directly up from the sink to the roof, then runs about 12' across floor, runs vertical about 10' to the basement floor, then runs under the concrete at about 1/2" per foot where it connect to the 4" PVC and this Coupling/Cast I am working on. I've attached some pictures for reference. I've checked the slopes 12 times, it's all sloped 1/4" or more heading into the cast.

The only thing I can think of is that I have not run any vents for the lines I'm adding for toilet, sink, etc. in the basement. Would this cause some suction from the main stack? I mean I don't have the vents connected yet...not that I'm not adding them. The vents can be seen in the pictures.

[drive.google.com]
[drive.google.com]
[drive.google.com]



Edited 4 times.

If you are upstream from any flushing toilets and you are getting water and debris, then the pitch is running downhill, then something is obstructing the flow and backing up. It would be a very good time in this case to get a video inspection to make sure there isn't a problem 10' from where you are working before you backfill and concrete everything in. You may also want/need to clean the main sewer line at the same time; the camera may not be able to get a clear view of the problem with standing water and waste in the line- it depends on the specific equipment and the talent of the operator. As for your leaking mission coupling, it looks like your 2 pipes aren't straight. It may be me, but it looks like they meet at about a 5 degree angle, and that may be pulling the sleeve out of alignment.

Thanks KC. I've checked the square cuts twice and have realigned the pipe a few times. The cast is pretty rough on the underside. I've cleaned it with a wire brush and grinder, but I just wonder if the seal is unable to be perfect due to cast. I think Silicone would answer that issue.

With the water/backup, water is pooling at the coupling. Like you said, may need to get the main cleaned and scoped. The "leak" is so minor, I wonder if it wouldn't happen if there wasn't water/pressure pooling there. It's only pooling there because that's as far as I've run the lines this far.

In picture #1, what's with the 3x2 sanitary tee on it's back? Not a legal use for a sanitary tee.

It's a vent for toilet on end of the 3" pipe. Haven't plumbed the entire line yet. Was making transition first. There will be a wall there from the exterior when framed.

It makes no difference what it is FOR, a sanitary tee in a waste carrying line is NOT a proper installation. It may seem irrelevant, but the codes are written to cover what you COULD do with that line some day in the future.

wear good nitrile gloves

slather it up with silicone

get clamp in position

remove gloves

tighten clamp

use a cardboard tube - pour tar around the joint

fuh-ged-bout-it

make the tee a y

==============================================

"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638



Edited 1 times.

Yep, changing that T to a Y tomorrow. Man, nobody said plumbing was easy. Measuring that 2" pvc perfectly in order to fit in a future 2x4 wall is tough enough, now I have to use a Y fitting and a 45. to go vertical? Humbug! I wonder if my inspector would have flagged me.

Well, good news on the coupling. It was some user error. I noticed when I removed the coupling that the bolts for the bands were pinching into the steel shield a bit. Of course this was directly where the two pieces of metal from the shield were coming into contact and it was enough to throw off my torque wrench. If I wiggled the bolts, I could easily hand tighten them further. When this was no longer true, I pulled out the torque wrench and tightened accordingly. NO leaks in 2 days. THanks for all the help and code violation notes. I'll try to report back with success once all complete.

As for the backup problem I'm having... that's another tale. I'm sending a camera down the line and guessing I'll find some roots in there. I was told this backed up a few years ago and they had to roto it out. Of course it drained exactly where I'm now working, so makes sense that I'm seeing the start of backup problems again.



Edited 1 times.

you could use a 'combination' Tee-Y



(not the right size, pic for eg. only)

==============================================

"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638



Edited 1 times.