What are my chances of unclogging a slow basement drain with a little Muriatic Acid ? I has seen plumbers use it before and they would just made sure they ran plenty of water down the drain after they were finished. Now bare in mind I'm talking about a home that was built in 1925 and there are about four different floor drains in the basement and they all drain fine except one we have been using for our washer drain and of course they are cast iron drains . The drain that is slow is only about 25 to 30ft long and runs into another line under the poured cement floor that runs fine. I have used snakes in all clean outs which I am so thankful for but this drain well I'm going to say all drains are static and getting any kind of snake in them is beyond me if I can take a picture of them I will and post here. Any comments would be taken with good advice and intentions. I found this on the internet and mine are the same just a screen over them.