Ask the Remodeler: Their cast-iron pipes are cracking

Q. What’s the best way to repair and maintain the cast-iron pipes in my 134-year-old house? We have had multiple waste water pipe leaks and are dealing with one now. Most of the plumbers we have contacted say it is an easy fix. They found a clear break completely around a pipe. Most of them have advised us to replace the pipe at the breakdown to the next connecting joint. One said to replace the whole section between the connecting joints (above and below the break), warning that if we didn’t, tremors or something like them could cause more cracks. Are tremors a real issue? If so, how serious an issue are they? This latest pipe break is near an exterior wall and runs from the second floor to the basement.

DANA T., Dorchester

A. I agree with most of your plumbers. I would replace either the section of pipe that is broken or as much as you can, including the various joints that connect to branch lines. Replacing as much as you can in one shot is a far more cost-effective way to deal with what will no doubt be an ongoing problem. Every time you have to do a repair on what sounds like a main waste line, you’ll probably have to shut off the water to the whole house. How often do you want to do that? Part of the problem with cast-iron pipes is that you often cannot see the damage until it cracks; they will rot away from the inside. This leads to an emergency repair, which can be costly. Regarding tremors, I would not factor them into your decision-making. We do get them every now and then — we did feel the April 5 earthquake, and nearby construction could cause them — but in all my years in the business, I have yet to see tremor-related damage to any part of a house.

Q. I have all-electric heat and everything else, and I’m paying a fortune. In 2019, I put in a heat pump to augment the baseboard electric heating. I have nothing in my attic but the air handler. It’s a huge attic and it’s cold. I’m not going to insulate it because that would be difficult. The attic is a concern because the ductwork tubes (about a foot in diameter) come down to the floor of the attic and then open up into the living space of each room — big, round openings. I’ve been told there is no way to insulate that ductwork. Is that correct? What can I do?

P.B.

A. Two things here about insulation. One is that you absolutely need to have those heat ducts insulated. Not only should they be insulated, they should be air-sealed with a mastic sealer or metal tape at all seams and connections. The mastic sealer is best. Once that is done, the ducts absolutely should have duct insulation wrapped around them and taped at the seams. You will lose a tremendous amount of heat otherwise. You mentioned how big a project insulating the attic would be. It can be a rather involved project, but it does pay high dividends. The air handler in the attic will be working extra hard in the extreme cold, and by definition, this will take years off the life of the equipment. We always strongly encourage insulating the roof and walls of an attic if any type of HVAC equipment is up there.

Mark Philben is the project development manager at Charlie Allen Renovations in Cambridge. Send your questions to [email protected]. Questions are subject to editing.