I have an old house with a drainage field. The problem is in the basement drain. The toilet in the basement has not flushed properly for a while and when the washing machine drains there has sometimes been back up in the floor drain. Today there was very black discharge from the floor drain onto the floor and the water is now only a couple of inches below the floor in the floor drain. There is no strong sewer smell.

There is a newer sink in the basement which drains fine and the main floor bathroom works fine. I had the main line snaked through the clean out and there was no clog found but when looking down the clean out there was water about 15 feet down the main pipe. Running water down the basement sink or even flushing the toilet has no effect on the height of the water in the floor drain.

Your main sewer is clogged. Have it snaked.

I had the main line snaked a week ago and no clog was found.

If your floor drain overflows when washer is used that means your drain is either Undersized to accept all the water form the discharging washer or/and it has some kind of build up inside the pipe making the drain smaller than it was when new.

Was it always doing or it just started ?

Since you probably cannot upgrade the pipes to larger diameter, you have to make sure the drains are clean to accept all the draining water. Otherwise, water will back up through the drain.

The "mysterious" black stuff that comes up from the drain is probably sludge build up that is part of the cloggage.

By saying "snake the drain" I mean to snake it the right way with right size tip. If you use wrong size tip, you will just poke a hole in the middle of the drain and leave rest of the sludge there. You could also have your drains Hydro-Jetted.

See the enclosed photos of typical drain with sediment build up. Unless that sediment is completely removed, drainage problem will continue...

Thank you for your patience.

I had the main line snaked with one of those huge snakes with the cutter tip. We had roots about ten years ago and I thought it might be the same thing but they found nothing. They did not snake the line going from the toilet to the sewer, or the floor drain, just the main drain through the cleanout in the basement floor.

Yesterday night I flushed the toilet and it flushed fine but this morning it is slow again. I did a load of wash to see what would happen and watched in the floor drain (where it had backead up before) and there was not a ripple when it emptied. There is still a problem though because the toilet does not flush properly again. Flushing the toilet has no effect on the floor drain at all and it has never backed up as a result of that, even when I flushed it three or four times to check it.

I figure I have to get the line from the toilet to the sewer and the floor drain snaked. Those pictures are amazing.

Could the black sludge be from years of build up in the floor drain?

Sorry, I should have said that the toilet has been inconsistent for a few months but it was fine before that and that the washing machine has been find until just the last couple of weeks.

What is hydro jetting?

I would suggest that they snake the line through the toilet opening. They will have to remove the toilet and snake it through there.

Washer and floor drain connect with toilet sewer line. But, there is a chance that Washer connects into Floor drain pipe BEFORE it reaches toilet line. In this case, and depending on how the drains were originally laid out - plumber would have to snake this drain from the floor drain opening or through the washer pipe.

I do not know where your existing clean out is located in relation to the rest of the bathroom fixtures. It is possible, it is not positioned behind the blockage but before it. Therefore it is in this case ineffective.

Hydro-Jetting is a type of drain cleaning service. Serviceman will use high pressure hose inserted inside your drain to clean it with pressurized water stream. This machine shoots water under extreme pressure and cleans just about everything what's inside the line. It is very effective for sludge build up. See the visual bellow...

Yes, sludge accumulates over the years and consists of body oils, soap residues, hair, bio-waste etc.

I think what you are saying makes sense as the washer definitely does connect before the toilet does. The only thing I can figure is that the clog is somewhere near where those join the main drain... also... it may be a perfect storm and I may have two clogged lines going to the main line.

Thank you for your answers. I will let you know if this works.