I have read that flushing a glass full of rock salt down your toilet every month is good practice if you have a cast iron sewer line. Reason being is that the salt will kill off any tree roots in the pipe and also prevent more roots from coming in and causing blockage. Is anyone currently doing this and if so how has it worked for you?
I was able to find a reference to this in chapter 22 of The Complete Idiot's Guide to Household Solutions.
Though honestly, I've never heard of this approach until now. I'm no expert on the corrosiveness of salt, but I would imagine the levels of salt in the sewer would not be high enough to rust the pipe. I'm also skeptical that the salt levels would be high enough to completely kill and prevent the roots. While I wouldn't recommend pouring a bag for rock salt down the drain, a handful once or twice a month will probably not hurt the pipe.
There are other tried and true methods to remove roots from sewer lines.
Augers can be used to effectively remove roots from a sewer line, by cutting the roots out. This is not likely a solution for a DIYer, since it involves expensive specialty tools. This method will not prevent roots from growing back into the sewer.
A hydrojetter is essentially a power washer with a rotating mechanical "sweeper", that is designed to be fed into the sewer line and blast and sweep roots away. Again, this is not likely a DIY option and does not prevent the roots from regrowing.
In some cases roots may have caused too much damage to the sewer line, and the only option available is to dig the line up and replace it. This can be very expensive, and will almost certainly not be a DIY project.
Contact herbicides are chemicals that will kill the roots, and in some cases prevent them from regrowing. These are typically a more DIY friendly option, and can be found as simple "pour down" solutions.
Contact herbicides can include:
A common product recommended by plumbers is RootX. This is a herbicide in a foaming carrying agent, that allows the herbicide to reach roots at the top of the pipe. RootX uses Dichlobenil, and is non-caustic, non-fumigating, and non-systemic. Unfortunately, it's not readily available to homeowners, so you'll likely have to contact a plumber for this treatment.
Searching around, I stumbled upon a product similar to RootX that is available to homeowners. Roebic® Foaming Root Killer is available at Lowes for about $20.00. It foams up, and uses dichlobenil as the herbicide just like RootX.
Make sure you check with your local municipality and environmental agencies, before pouring chemicals down your drain
One of the best ways to prevent roots from entering your sewer line, is to carefully plan where you plant trees and other deep rooting plants.
I have never done this. The first thought that comes to mind is an auto from the "rust belt" where rock salt is used to treat icy roads. the result is corrosion. I would think that the pipes would be damaged. If you don't have municipal sewerage I don't see it being healthy for your septic system.
no its gonna be bad in the long run----a lot of piping underground is made from cast iron---the salt water will be an electrolyte and it will eventually eat the pipe ,atom by atom (or ion by ion ) if your piping is plastic based it connects somewhere to a cast iron line----if you flooded the soil around the outside of the pipes it would (i think ) keep roots out of the pipes but then again you have the galvanic reaction with the salt water acting as an electrolyte
I would venture that a cup of salt once a month would have no effect, considering the amount of waste/water also flowing through the sewer line. Don't bother.