So far I replaced all of the fresh water galvanized pipes.  The rest of the potable water is mostly copper with a few pieces of pex.  The question I have is really on the waste water side.  Which is almost entirely cast iron.  There are two or three small sections of galvanized in there that I need to cut out and replace on the shower waste water side.  And on a bath sink.  


My step brother owns a bunch of rentals that are older and he recommended that I put a cleaner down the waste water pipes about once a month to keep them free from buildup.  He recommended so powder based cleaner sold on Amazon.  Can’t remember which one.  Anyways.  I’m wondering if this is good advice or if this will cause my cast iron to wear prematurely?  

Any thing I should be doing regularly on my cast iron to keep it maintained?  Oh and I have no idea where the main clean out is.  This is a 1 story ranch with full finished basement (drive out basement). 3 full baths, 2 up 1 downstairs.  Washer dryer in basement on same wet wall.  The only separate waste water pipe comes from the kitchen sink on the far garage side of the house.  Wet wall is in middle of house.

Cast iron will corrode. I wouldn't think any type of "additive" could possibly prevent that because it won't sit in the pipe long enough... because it drains.

If your sewer pipes are easily accessible I would just say replace it as it goes bad with PVC and Fernco's. If you need a clean out cut in a wye and a cap.

Cast iron is a PITA to cut with a Sawzall, but they make blades for it. Using chain cutters is preferred but that can crack and collapse older pipes.

How about a diamond blade on the cast iron? They seem to do well on everything else.

Replacing the piping above grade is not a problem.  The below grade stuff will be a challenge.  But it’s not like the cast iron is in bad shape yet.  

I’m really more curious if putting some kind of draino or other pipe cleaner down periodically will help keep the pipes moving…..but don’t want to deteriorate the pipes prematurely

I just paid a plumber to replace a section of cast iron and galvanized drain pipe in my 1950 ranch house.

He told me do not use the common drain cleaners. He did recommend a heavy dose of Dawn dishwashing soap down the kitchen sink drain and follow that with hottest water you can get. He didn't give me an specifics on how much or how long to soak before flushing with hot water.

Yeah, I worry about Greasy residue gumming up the kitchen drain pipe.  It’s only a 2” and runs a fairly long way.  Pvc from the sink to the basement floor, then turns into cast iron and runs horizontally under the slab toward the front center of the house. It’s clogged before.  I put a pvc clean out at the pvc to cast iron transition.  Have had to rooter in with a 25’ rooter a couple of times and then used green globber overnight once.  Cleaned up fine.  

Dreading the day I have to saw cut the slab and replace below grade cast iron