I have had a septic for 20 years and I use Scotts regular. This is the brand that was recommended by a plumber and my septic guy. It is like using sandpaper on your skin but it doesn't clog the septic. You can see for yourself if you wet the Scotts it immediately falls apart. You can look at other brands and just put some water on them and see how fast they break up or just go with tried, true, rough and cheap Scotts. When my kids complain I just tell them that when they use a puplic restroom they will fell more at home because the paper is usually equally as rough as the Scotts.

Have the tanks pumped out by a licensed septage contractor. You then can run water from the house to observe what is happening. It sounds like the baffle between tank is plugged. If everything is working properly there should NEVER be any solids in the second tank before it goes to the field or is pumped up to field. Your "Field" is probably an engineered septic field. RJ

Thanks Klem1, our laundry grey water system is not connected to the septic lines so no problem there. And normal water use does not cause problems as the septic system works perfectly 95% of the time with the exception of prolonged very heavy rainfall such as 2" one day then again 2" the next day (twice/year on average now). This system has a distribution box with 6 leach lines extending about 75' each. As for trees, there are 2 Paper Mulberry trees that have notorious root systems that have surely disrupted at least 2 of the leach lines and that's no help for sure. This spring once things are dryer I will consult a specialist for pricing the replacing at least the 2 lines nearest the trees. The ground over the leach field is high ground and doesn't puddle water thankfully. The only reason the lower toilet burps when the upper toilet is flushed is because the lower toilet is vented with a studer vent which allows air intake but does not let air out (unlike a roof vent which does both). If the lower toilet was vented thru the roof it would not burp and I wouldn't know that waste water could be backing up into the line from the house until it was too late. I hope that makes sense, ha.

Low consumption toilet is definatly a good thing for the septic system. On the other hand,garbage disposal,,exccessive fats,dis-infectants and other chemicals are bad.