You naysayer people sure are dreamers as very few RV's that would be dumped into a home septic system have any where near 100 gallons in them. What an explicit exaggeration!
Follow closely:
To begin with, you first open the black tank valve and dump it completely which isn't a one minute task! Then you close the black tank valve and open the gray valve and dump it which then flushes and rinses the dump lines and the outlet valve area. Any RV'ers with half a brain wouldn't dump both tanks at the same time as the whole dump system would stink like mad in a couple days max in warm weather! How much is actually dumped? Usually only 30 to 40 gallons max in each tank when dumping and at home, it's you that controls how fast the total dumping is done and remember that there's not even one other RV behind waiting for you to get finished.
Still nervous about dumping your RV into your septic tank? If it makes some of you feel better, simply dump the black first as fast as you desire, wait an hour or even more, and then dump your gray water as fast as you desire! DUH, consider it solved! See how simple that is? Regardless, even if a total of 100 gallons is dumped, it's only 1/5 to 1/10 of what a home septic system is designed to handle each day and your dumping the RV at home isn't done each day but maybe a few times during each season! Such lame exaggerated claims exhibited by a few on this thread!
Even full hookup RV'ers are certainly smart enough to keep their dump valves closed until it's time to dump the tanks. At which time, they dump their black first and follow with the gray! WALLA! It's gone and now they close the gray valve!
On top of all of that, only a small fraction of what the RV holding tanks contain even when totally full is RAW SEWAGE. Most RV's total combined tanks dumped contents is shower water which contains a small amount of soap which is not raw sewage. The second in content is dishwashing and rinse water and also contains soaps. Then comes face and hand washing etc waters and more soaps. Finally we get to "black water" from the toilet which contains some raw sewage and tissue (TP) and a very large percentage of clean rinsing water.
FWIW, just looked at our Amanna washing machine manual and the manual says 8.3 gallons for large load wash and 8.3 gallons for each rinse cycle. That's 32.9 gallons for each and every load washed and rinsed alone and DW says we average 7-8 washings a week. We virtually always wait until we have a full load before washing and why not? Yes, we do like and demand clean clothes on totally each and every day after our showers and more clean clothes on when we go out to eat etc at night and aren't about to change. I've/we've noticed and so does our noses and eyes that many people tend to do elsewise! Remember that you must include washing all sheets and blankets which we do more than once a week! When in the RV for over a week at a time, there's nothing like using a decent laundramat and getting all the washing done very fast and cheap too. Usually takes about 1-1/2 hrs each week to 10 days. Big deal! Then there's the showers and baths, the dishwashing and toilet flushing, hands and face washing, etc!