[DutchmenSport]

Originally Posted by beeje

...It is after all a waste tank, there is no need to get it sparkling clean.

I've been using one of these Flush King style valves on 3 different trailers now. How many "back flushes" does it take to get the black tank "sparkling clean?" Answer ..... 15.

Every year, this is part of my winterizing process, to clean the holding tanks as much as possible. I can do this at home, with the ability to dump and to add water is no problem.

One year, I decided to REALLY clean out the black tank. So I kept adding water to the shower drain, filling up the grey tank. I can back flush 3, sometimes 4 times with a full shower water grey tank. And that year I took photos of every flush so I could actually see the water get clearer and clearer. It was 15 back flushes before clear water came out of the black tank.

This year, I back flushed 3 times. I then used a toilet wand. And I also used the black tank flusher system. I used approximately 150 gallons of water to flush out the tank till water ran clear.

How do I know how much water I ran? I dump into my 32 gallon Barker Blue Tote and dump it in my septic tank. It took 5 trips to the septic tank and the tote was full each time.

For those who say all you need to do is fill your tank and dump and you are good, you really should try back flushing with the 3rd attached valve. The first time you do, and you see how much MORE "stuff" comes out of your black tank, you WILL be a believer and never feel comfortable again, just dumping once and running!