I live in a 2 year old slab home with a septic system and drain field. There are three of us in the household. We have 3 toilets (2 downstairs) and three showers (2 downstairs). The toilet closest to the septic system has recently (past 4 weeks) had very slow draining after flushing. I snaked the toilet, found no blockage, then removed the toilet and searched for any blockage in the toilet - there were none.
The exposed pipe had no water backed up in it - I did not snake it. I replaced the toilet and had the same slow draining issue. The other toilets flush and drain as they should.
I have also noticed when I use the washing machine or take a shower that the water bubbles in the 2 downstairs toilets and sometimes almost drains away completely.
Is my septic system full?
Do I have a blockage somewhere?

I have also noticed when I use the washing machine or take a shower that the water bubbles in the 2 downstairs toilets and sometimes almost drains away completely.
Is my septic system full? I would check the septic tank and drainfield. Bubbles indicate a partial blockage causing a blowback of back pressure that produce bubbles. The sucking out of the toilet bowl is a classic indication of a blocked vent. Are the two bathrooms back to back? Sounds like you might have more then one problem. Back to you, Tom

The 2 downstairs bathrooms are not back to back - one is in the master bathroom on the furthest end of the plumbing line, and the other is closest to the septic system. The bubbling problem is not constant, but didn't happen prior to a few weeks ago. The backup issue on the toilet is a constant issue and that one is closest to the septic system.

I asked about the two bathrooms being back to back because of the bowl levels being sucked out when the washer discharges. This tells me the system's attempting to vent through the toilets. I think you have two problems. I would, at the very least, open up the septic tank and check it out. I would also have the washer vent ckecked for a blockage. Regards, Tom

Toms is giving the best advice here. Start by checking, or having septic tank checked. Then we will go from there. Please let us know what you find.

I opened the septic tank today and cleaned the effluent filter and all seems OK so far. The backed up toilet is working normally and I have not yet heard the bubbling with heavy water use.
Thank you for the suggestions.

Excellent! Keep us informed. Tom