Cast Iron P-Trap Under Bathtub Collapsed

Hello Folks,

I have an old cast irn sewer line under the house, some portions of it are galvanized metal though. There is a main bathroom for the house whose bathtub p-trap (as seen from the crawlspace) has collapsed and cracked open, as shown below:



I have known about the issue for some time now, but I have postponed addressing it due to the fact that the going through the crawlspace a dreadful experience for me. Since it is contaminted with sewer and other stuff, I will lay down a new plastic there and use a body vest+respirator.

Any ideas on how to to approaching cutting the cast iron (reciprocating saw with special blade?) and going about fixing the whole thing (I wish it was PVC, life [specially under the crawspace conditions] is so much easier with PVC's cut+coupling+fitting then prime+glue approach.

Another option would be to do it from above, but I would have to remove the bathtub and then destroy the bathbut surroundings along the process.

A metal cut blade on a re-sip saw will make quick or of it. Where I live it would be abs all glued joints and a clamp on rubber adapter to the cast iron.

Use a garden hoe and pull out as much bad soil as you can, under the house is not a good place to leave it.

Cut as much of the galvanized out as needed and replace with ABS. Use a rubber Fernco type coupler to convert from ABS to cast or galvanized.

That is an old mess you have under the tub ... but it can be repaired if you like to play with tinker toys.

You should take your pics to the Home Depot or plumbing supply. They can direct you where to cut with your sawzall, remembering to leave stubs long enough for your Fernco attachments.

The new p-trap and piping will be ABS and glued accordingly. Work this out by dry fitting everything first so your angles and lengths are correct. Then mark the ABS fittings with a Sharpie so you can add the glue and properly position the pipes. ABS glue is extremely strong so get your pipes in place then let them set up for 10 minutes.

Here is a simple video on how to use Fernco connectors. They are really how professionals handle situations like yours. Best of luck ... and take the "after" pics so we can see how well you did!

[ame]http://www.youtube.com/watch?v=EFaJyIzyiYA[/ame]

And here is a guy actually doing a new connection after taking out the old cast iron. FYI, the angle grinder is really efficient in tight spaces. His tip about a full face shield is good advice.

[ame]http://www.youtube.com/watch?v=zZHtHBLcUhY[/ame]

Hello Again, and sorry about the long time span for this follow up... I have been away, but last week I managed to get some work done. Firstly, all the plumbing below the bathtub was replaced and renewed (old was cast iron or galvanized and the linkage+stopper for the drain was broken, etc). The pic below shows the new pvc plumbing right under the bathtub and the aggravated cast iron + galvanized plumbing in the crawlspace further below the tub:



I bought a rather expensive diamond blade for my reciprocating saw and then cut the broken section, but afterwards it turned out that I would not be able to remove galvanized fitting from cast iron tee due to corrosion (the plumbers wrench would fragment the corroded metal on the surface of the pipe), so I went ahead and cut further and in in the threaded galvanized fitting:



As seen from the above the galvanized pipe did rust from inside quite a bit, to the point the whole interior of the pipe was filled with rust. Also, the diamond blade seem to be good for one cut only (the second cut took forever to finish) -- next time I will try to cut the cast iron pipe with my plasma cutter just for kicks!

Once everything was cut, cleaned, and deburred; I went ahead installing the rest of the pvc plumbing and used the fenco to make the connection with clamps as shown below:





After tightening down the clamps at then fenco and the drain in the tub itself, it seems that there are no leaks. But then there is another problem: it seems that at some in the old cast iron (or galvanized) pipe there is a clogged, and I suspect that the thing may be full of corrosion if the corrosion saw at the pipes removed foretell the worse. Maybe the dissimilar metals (cast iron and galvanized) promoted too much corrosion.The end result is that the water is draining extremely slowly...

http://www.improvementcenter.com/plumbing/plumbing-parts-how-long-before-replacing.html
If the house is 60 years old it might be time to think about the whole system.

You might try filling the tub completely before opening the drain to let it flow out. The volume of water plus the force of the full tub-full may be enough to flush the pipe. Of course, if it doesn't help, it will take a while to empty the tub. You also have the choice of removing the Fernco fitting and running a snake from there.

nealtw said:

http://www.improvementcenter.com/plumbing/plumbing-parts-how-long-before-replacing.html
If the house is 60 years old it might be time to think about the whole system.

Click to expand...

Yep, the house was built around 1955; but at first it had a septic system and was not connected to city sewer till the mid 70s. So, maybe the plumbing was retrofitted at some point. Most of the plumbing seems to be working just fine though (so it is not a generalized issue). It seems that they have replace cast iron parts with galvanized steal at some segments thus accelerating the decay/rust of the metal 100 times fold.

slownsteady said:

You might try filling the tub completely before opening the drain to let it flow out. The volume of water plus the force of the full tub-full may be enough to flush the pipe. Of course, if it doesn't help, it will take a while to empty the tub. You also have the choice of removing the Fernco fitting and running a snake from there.

Click to expand...

I tried filling half the tube and now a remainder (about 5% of the tubes's water capacity, and not half of it) of the water would not drain at all. I also put concentrated bleach. Give that there is lots of bleach+water stationary in the pipes it will be more difficult to remove the Fernco in the crawlspace and avoiding been hit by water+bleach. But, yeah, Fernco removal is my next step, otherwise I will cut further and replace with PVC.

I suggest, you go back and replace as far back as you can go.

tk3000 said:

Yep, the house was built around 1955; but at first it had a septic system and was not connected to city sewer till the mid 70s. So, maybe the plumbing was retrofitted at some point. Most of the plumbing seems to be working just fine though (so it is not a generalized issue). It seems that they have replace cast iron parts with galvanized steal at some segments thus accelerating the decay/rust of the metal 100 times fold.

Click to expand...

Any updating in the 70s would look much like what you have done with the tube.
All that pipe is original.

nealtw said:

Any updating in the 70s would look much like what you have done with the tube.
All that pipe is original.

Click to expand...

Ok, I got the idea. But my condo was built in 74 and the sewer lines coming from underground are cast iron. But the drain pipes around the unit have all being replaced with pvc at some point in time.

Cast iron is still used today as it is less noisy but I am surprized they were still using galvinized in the 70s.

This particular portion of the drain under the bathtub goes down straight to the main sewer line which then exits the house as seen in the pic below:


Arrows point to main sewer line exiting the house. So unless I cut through the main plumbing line, I can only go so far.

To aggravate the situation this drain is directly connected upwardly to the vent stack which also is cast iron. And in order to easily connect new pvc there I may have to break through walls as well. Shown below:



In case I cut off the elbow out, then there would be two fernco couples up and down connecting the new pvc elbow and some pvc fittings to the cast iron, but there is no clear cut spot to connect the fernco in the upward portion (vent). Thanks for any inputs!

Will that vent also be the drain for the bathroom sink?

nealtw said:

Will that vent also be the drain for the bathroom sink?

Click to expand...

It is just a vent stack for the plumbing that happen to be directly connected to cast iron elbow which then also connects to the bathtub drain, so if I replace the elbow with pvc there will be a need to use another fernco couple to connect the upward vent... It just difficult to reach, and there is mess with foam spray, but I should be able connect the vent with fernco as well

I am not sure whether or not it will be a vent to the bathroom sink, I will try to find out but I believe that the sink has its own vent stack. Is it really necessary to have so many vents?

I was thinking that if the sink drains into that vent and it drains good, that might tell us something.
If the sink has a separate drain and vent you could maybe remove the whole pipe thru the attic or roof and replace it with out cutting into walls, if replacing it is required. If not what is on the other side of the wall from the bathroom, cutting into a bedroom wall or closet wall would be easier than the bathroom.
We often see vents tied together in the attic so they have less holes in the roof.
Every fixture needs a vent within so many feet of the fixture.

tk3000 said:

It is just a vent stack for the plumbing that happen to be directly connected to cast iron elbow which then also connects to the bathtub drain, so if I replace the elbow with pvc there will be a need to use another fernco couple to connect the upward vent... It just difficult to reach, and there is mess with foam spray, but I should be able connect the vent with fernco as well

I am not sure whether or not it will be a vent to the bathroom sink, I will try to find out but I believe that the sink has its own vent stack. Is it really necessary to have so many vents?

Click to expand...

simple explanation of a vent.

fill a glass with water, put a straw in the water
put your finger tip over the end of the straw and pick it straight up.
the water stays in the straw. no vent
take your finger off the straw. vent

with out a vent, your pipe will not drain

frodo said:

simple explanation of a vent.

fill a glass with water, put a straw in the water
put your finger tip over the end of the straw and pick it straight up.
the water stays in the straw. no vent
take your finger off the straw. vent

with out a vent, your pipe will not drain

Click to expand...

Thanks for the explanation. But I know that drain fixtures need to be connected to a vent stack to avoid air stream from creating a vacumm within the system, but the question I posed was whether or not one would need one stack going to the roof for every fixture, or maybe few fixtures could be connected to one vent stack (directly and indirectly connected).

nealtw said:

I was thinking that if the sink drains into that vent and it drains good, that might tell us something.
If the sink has a separate drain and vent you could maybe remove the whole pipe thru the attic or roof and replace it with out cutting into walls, if replacing it is required. If not what is on the other side of the wall from the bathroom, cutting into a bedroom wall or closet wall would be easier than the bathroom.
We often see vents tied together in the attic so they have less holes in the roof.
Every fixture needs a vent within so many feet of the fixture.

Click to expand...

Yeah, maybe I could try approaching from above in the attic or from below the close. From inside the bathroom I would have to break through cultured marble panels, an iron bathtub, etc... But first I may try to use fenrco to connect it to a new pvc elbow from below.

I bought some cheap carbide reciprocating saw blades to cut through the cast iron plumbing (Diamon is a one time use only, the next time takes forever to cut..., so it is not cost effective)