Greetings,

I live on the bottom floor of a 45-year old, 16 unit 4-story condo.

I have had no other drain issues at all, ever... until I bought a washer.

The unit had a space for a stackable washer/dryer & I have a dedicated washer box and drain line that goes down to a metal "T"?
When I tried to drain my new washer, it quickly spilled back over the drain opening. After shutting the machine off, the water slowly drained but there was a small amount of 'stink' water I was able to shop-vac out (trap?)

When I tried to run a sink snake down it, the snake quickly stopped and did not seem to want to make a turn like a trap does, but like the attachment was a dead stop at a "T".

My 86 year old Father-In-Law, a retired plumber, told me to pour in a full bottle of "CLR" and let it sit for 2 days and then try the line with a small amount of water as to not overflow the pipe. His theory was that since my A/C condenser drains into the same line about 2 feet away, the A/C drain may have scaled up the trap over the years.

I asked him "what if that doesn't work?" He said we will need to open up the wall... clank!

Any other ideas?

Thank You in advance

Dean