Is it possible for a 3 year old septic tank to be full already? The sink started gurgling when my daughter flushed the toilet. I went outside and opened the cleanout valve and noticed standing water. I checked for leaking toilets, etc... Nothing unusual found. Of course, my wife did 3 loads of laundry, but that has never caused the 1200 gal tank to backup.
It is possible that your tank is full, but if it is you have some problems. You didn't mention what the load on it is, but a 1200 gallon tank should be good for a family of four if you have a good leach field in good condition (which, for a relatively new tank should be the case). If you have a lot more "load" on it I guess it could fill up...
Three loads of laundry shouldn't be an issue. Any chance you have a clogged up sewer line leading to the tank? Something to check.
Are both compartments on the tank full?
Is it a pumpout system or gravity system?
Leach field or mound?
Have you had lots of rain this year?
Has the tank ever been pumped out?
We have 2 adults 2 toddlers in the house. Laundry is the most common source of water usage since our kids play outside with the animals...
I have a gravity system with leach field. The soil is sandy, and so is the native soil. Normal Central Florida soil.... We have had lots of rain, but not out of the normal for this area. We average 60 inches per year.
Septic tank was full. The septic guy said 3-5 years was not abnormal for a tank to fill. He noticed that I did not have a right angle on the pipe which would have kept the fluid moving under the crust. He said there were pros and cons to the right angle on the end of the pipe. With the right angle the water level can push the crust too high which could allow solid material to get into the drain field. Without the right angle the tank fills up faster and the crust layer will be thinner...
Most tanks have water to the brim anyway. The sludge settles in the bottom and the fluids flow over the top of the tank into the leach field.
Of greater concern would be the nature of the "solids" in the tank. Your gurgling sink made me wonder whether you have a garbage disposal. If you are sending "uprocessed" food into the tank then the sludge level may not be able to work fast enough for the load.
Also, is your washing machine attached? Dumping large of amounts of bleach into the system will kill the bacteria that you need out there to process the sludge.
If you have the guys come pump the tank, ask about how deep the sludge level was and whether they think the bacteria are working properly. They will try to sell you an overpriced jug of bacteria, but it's better than nothing to get the tank going again.
If the largest contributor to the septic tank is the laundry, check with your local health department to see if they permit laundry waste water to be drained separate from the septic tank, and what their requirements are for a dry well or cess pool for the laundry waste water. Many counties in Florida allow the gray water from a laundry to be drained separately. This might be as simple as attaching a longer hose to your wahsing machine that will drain outside.
In our case, I hooked the washer drain hose over the side of a laundry tub, then set a large bucket inside the tub. Much of the waste water gets caught in the bucket, which my wife then uses to water her herb garden, right outside the garage door from the laundry area. The plants seem to love the soapy water; we don't often use bleach.
Something strange here.... After having my septic tank pumped out, I am noticing some strange odor coming from the shower. We had it pumped about 3 weeks ago, now we smell a mildew type dank odor coming from the walk-in shower drain.