Home>Discussions>PLUMBING>3 Inch Cast Iron Drain Pipe to 3 Inch PVC at Coupler slight leak?
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dj1
Re: 3 Inch Cast Iron Drain Pipe to 3 Inch PVC at Coupler slight leak?

If the cast iron is not smooth, you can sand it a little bit, just enough to give the coupling a chance to wrap it completely. If you want to use a grinder, go slow and don't over do it.

HoustonRemodeler
Re: 3 Inch Cast Iron Drain Pipe to 3 Inch PVC at Coupler slight leak?

In my fair state all buried connections must have the metal band.

dj1
Re: 3 Inch Cast Iron Drain Pipe to 3 Inch PVC at Coupler slight leak?

Regarding the size of the 3"x3" coupling: I'm not 100% sure, but I think that they only make a coupling that's 2-1/4" long.

MMeehan
Re: 3 Inch Cast Iron Drain Pipe to 3 Inch PVC at Coupler slight leak?

Okay thanks I will go and get another Coupler (it has the band now) and sand down the cast iron pipe and get it smooth and hope the coupler will seal it tight enough to end the leaks...

Just wanted to be sure they did not offer one longer maybe 3 inches in length to get more to attach and seal the cast iron pipe where it is leaking...

MMeehan

dj1
Re: 3 Inch Cast Iron Drain Pipe to 3 Inch PVC at Coupler slight leak?
MMeehan wrote:

Okay thanks I will go and get another Coupler (it has the band now) and sand down the cast iron pipe and get it smooth and hope the coupler will seal it tight enough to end the leaks...

Just wanted to be sure they did not offer one longer maybe 3 inches in length to get more to attach and seal the cast iron pipe where it is leaking...

MMeehan

I see your point, but a leak is a leak, and a longer coupling will not stop it if a shorter coupling didn't.

MMeehan
Re: 3 Inch Cast Iron Drain Pipe to 3 Inch PVC at Coupler slight leak?

Well if it was longer it would have more to seal off the 2 different pipes so if it has 3 or even 4 inches to seal up and against the 2 different materials pipes it might get a "better" seal with more contact on both pipes since I would have never thought it would even leak just like another thread asking how long they last some suggest 40 years when underneath cement well it sometimes does not last that one mine did not maybe 8 years and now I have to see if I can correct this because I thought it would last 30 maybe longer and it did not make 10 years... And ir was installed by a plumber so I thought it was good for a long time but it is not...

MMeehan

dj1
Re: 3 Inch Cast Iron Drain Pipe to 3 Inch PVC at Coupler slight leak?

It would be impossible to say why your coupling failed after only 8 years without seeing it.

MMeehan
Re: 3 Inch Cast Iron Drain Pipe to 3 Inch PVC at Coupler slight leak?

Thanks but if the PVC is hanging down about 5 ft and the cast iron is straight up and solidly in place and again both are behind a 2 tub cement sink so I see it hard to see when the plumber dry fit all the pipes in place to be sure they were aligned mark all pieces and the assembled them in place. I watch trying to learn something for future issues. I rarely get within 5 ft of these pipes so I can only wonder why it did fail / started leaking. it is showing water stains down both sides of the cast iron pipe. about 2.5 inches apart one down the side of towards the open basement the other near the backside of the towards the basement block wall but not straight inline from each other. If it was just one spot I could maybe see it but it has 2 spots and when I wash the dishes or take a shower and return to the basement and have water running to the closest floor drain about 4.5 ft away. I checked the screws to see if they were loose but they appear to be tight and have not seen any specs as to how much torque / tight they should be tightened to? Maybe it was over tightened?

As for being longer if like a heater hose on a vehicle the farther it is on the connection seems to have a "better" seal one would think the same with a rubber coupler would have better sealing capability if it was an inch longer on each side of the pipes. As with any kind of liquid connection but again that is what I thought when asking about if there is a "longer" version of these Couplers... And when I had this done I thought about doing it myself but back then Couplers were only available from a "plumbing supply" and not any "big box" stores like they are now. I came across 2 3 inch versions P3005-33 & P3000-33 they appear to be similar and one is 2 dollars more than the other. I just hope to but the right one for PVC & Cast Iron. Appears now they have 2 back then I am not sure but maybe they only offer one for all pipe materials?

MMeehan

Mastercarpentry
Re: 3 Inch Cast Iron Drain Pipe to 3 Inch PVC at Coupler slight leak?

Fernco's aren't designed to span a large gap. The covered versions are intended for cast-to-cast connections and are called "Hubless connectors". If they fit you can use them with any pipes though. I'd want to see gap between these pipes at no more than about 1-1 1/2", even if that means extending the PVC. You may need more with the hubless fitting to get it on- just keep the final gap as small as you can work with. Sanding the cast is fine but a sharp coarse file will work a lot faster for you. I also like to use silicone caulking on the cast pipes where I put a Fernco. Smear that on and wipe all of it off that you can with a rag- enough will remain in the voids to allow for a good seal to be made without having so much that the Fernco slips off. I tighten these with a large screwdriver and good but not full strength applied, looking to compress the rubber well but not to greatly deform it. There is a torque spec (and a special tool made to do this with too) but I find my method works fine.

Fernco's are rated for inaccessible locations when installed correctly, so they should last for at least many decades- I've never seen one fail except for when over or under tightened or with pipes shifting around. They should not be in direct contact with concrete which is corrosive due to it's alkaline nature, nor should they be used when proper connections can be otherwise made. I wouldn't be without them- they are a godsend to plumbing repair work.

BTW, the guys behind the plumbing supply counter usually know as much about plumbing as those who do the work- they hear all the stories and are quite happy to share their knowledge and sell you the right products. About half of what I know of plumbing came from these guys. Tell them of your plumbing problems and they'll tell you how to fix them properly- you'll never get that kind of knowledge from sales staff at a big box store.

Phil

MMeehan
Re: 3 Inch Cast Iron Drain Pipe to 3 Inch PVC at Coupler slight leak?

Thanks the gap between the cast iron pipe and the PVC is maybe 1/2 inch if not less. The cast Iron as paint on it has for many years prior to me buying the home...

You are the "first" to suggest putting kind of sealant or anything on the cast iron pipe. This is interesting no one has suggest that.

Have the new Banded Coupler as the one prior look to be the same just have to pick up some fine or medium grit emery cloth to sand the cast iron pipe just to be sure it is smooth. My local HD did not have it, going to hit an auto parts store, check several HD in the area and none carry the emery cloth. Guess they just don't have the demand for it though you see plumbers using it to rough up copper pipe and fittings to get any thing off the pieces.

Once I have the emery cloth and pulled the old coupler off. I will install the new one...

And see if it works...

Thanks for the information....

MMeehan

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