Black Tank Flush - Do We Really Need This?

[JRTJH]

You should not have any problems overpressurizing the black tank using the flush system. If the tank wasn't vented properly (at least as far as pressure is concerned), there would already be issues with bubbling and gurgling when the toilet is flushed with anything over a half full black tank. Almost always, if there's an issue with inadequate tank venting, the toilet will "wet your knees" when you flush. Venting isn't something that just sneaks up on you. If there's a problem, it shows up in pretty dramatic ways.

Now a leak in the venting system, that could go un-noticed for a long time before it becomes a problem, but that wouldn't overpressurize the tank by using the No Fuss Flush system.

Usually (especially with a regulator on the hose) water flow in a 1/2" garden hose is around 3 gallons per minute. The spray nozzle further restricts water flow, so you really aren't filling the tank rapidly when you use the system. As a "kind of general rule", if you have a 30 gallon black tank, using the flush system, it would take about 10 minutes to fill the tank. If you really want to get an "accurate estimate" of your flow, START WITH A CLEAN BLACK TANK , hook up the flush system, close the empty black tank valve, run water for one minute, open the valve and drain into a 5 gallon bucket. You should be about 3/5 full. That quick test will tell you how long you should leave the flush system running with the valve closed to get the amount of "fill" you want in the tank.

Many people don't realize that the spray nozzle and the supply hose aren't capable of putting a "lot of water" into the tank in a short time. How much water really depends on your specific installation. If you don't know how fast your tank is filling, you are "best guessing" how you use it. By checking how much water you get in a given time, you'll know how full (or empty) your tank is while the valve is closed.

Of course, if you use the system "per instructions from Keystone", that would never be a problem.

[jje1960]

I've used the black flush since buying the trailer in Fall of 2010. However, just yesterday, I learned something on use.... Pay attention to the sticker that say's to only use with the black valve open. I was using our macerator yesterday to dump at home after a long weekend for the Morgantown romp of Baylor.... Anyway, I turned the black flush on before opening the black valve... Big mistake, clear water started running down through an access hole where all the lines run up to the bathroom compartment. I quickly turned it off, opened the black valve, started dumping as usual. After a minute or two, turned the black flush back on, no more water running down from above. Lesson learned, actually read and follow instructions!

[Javi]

Originally Posted by jje1960

I've used the black flush since buying the trailer in Fall of 2010. However, just yesterday, I learned something on use.... Pay attention to the sticker that say's to only use with the black valve open. I was using our macerator yesterday to dump at home after a long weekend for the Morgantown romp of Baylor.... Anyway, I turned the black flush on before opening the black valve... Big mistake, clear water started running down through an access hole where all the lines run up to the bathroom compartment. I quickly turned it off, opened the black valve, started dumping as usual. After a minute or two, turned the black flush back on, no more water running down from above. Lesson learned, actually read and follow instructions!

That's actually a backflow preventer and its plastic and the leak had nothing to do with the tank valve being closed.. Just coincidence... You can read this thread from the beginning and/or many other threads about the plastic backflow and the fix.. which is not expensive but an inconvenience when you think that for $5 more the manufacturer could make the fix unnecessary.

[greengiant]

I like the flush. I used to mess around with gallon jugs of water to dump down the toilet: some to try to rinse out extra 'stuff' , and some to dump down after its empty and closed so there would be water in there with the treatment stuff (maybe the treatment is unnecessary to begin with but that's a topic for another thread). In short, that was a pain.
New Hideout TT has the flush, and a bonus is a second entry door to the bathroom, so before I start dumping, I open the bathroom door, and I can wander around to check on the check valve to make sure there's no issue. If there's no line at the dump station, I do as others mentioned-close the black valve and let it fill a few minutes and then open back up to rush out extra solids. Is it necessary, certainly not. Do I like keeping the tank 'cleaner' and not messing with jugs of water-yes. Hopefully my second winter doesn't cause any issues if I properly blow the lines again.
Great topic.

[gkainz]

Mine seldom gets used, as most of the NF Campground dumpstations I visit either don't have a flush hose or those that do, don't have a threaded fitting on the end.

I do use it at home during the occasional dump cycles here. I have a sewer clean out next to my parking spot.

[DaleB]

First I would like to say to Festus that that 49 cent check valve he mentioned is actually on sale for $54.95. It should only be 49 cents because it is nothing but apiece of well actually junk as mine did not work from day one and flooded my bathroom. I called Keystone customer service and the Man I talked to was clueless as to what it was and he had never heard of any problems. Funny that when doing a search I have read off all kinds of problems with this part. Now I realize that the people answering the phones can not know everything but at least they should be able to transfer you to someone who does. For those of you that are not aware of what this devise is I will tell you that it is in place to prevent bacteria from entering the supply water that is used to back flush your tank.The vacuum breaker check valve is most generally located under the sink in the bathroom and is a black plastic looking thing with a line going in and a line coming out. Sometimes they are installed wrong at the factory.

[theeyres]

I have been RVing for 50 years. Yes, count 'em. I now have the flush system but never felt the need. Never had a black tank plug up. Never had problems with smell. Always thought the black tank was just a holding tank so no big deal. I just have to think this is all a big gimmick where everybody follows along. Give me another 50 years and I'll figure out if it is worth worrying about or not. For now, I'll dump when I need to and not worry about it. I'll just treat the tank as a holding tank and let it go as that.

[64tbolt]

Originally Posted by Tom

I look at the black tank flusher (this trailer is the first one I've owned that had it) as a handy item but not a necessary one.

It's puzzling to me how many users on this thread seem to be using it. I only use it when the black tank valve is open which means that there's no chance of any flooding problems. Doesn't seem like a good idea to use it with a closed valve which would allow pressure to build up in the tank. Of course If I had an assistant to keep the toilet valve open to prevent pressure buildup that would be OK. Seems pointless though since it does a good job with the black water valve open. JMHO

If I want to put water in the tank I always use the toilet to do so.

if the tank is vented how do you pressurize it. I installed one and use it every time I dump. Just have to be smart enough to not over fill the tank. Mine being an add on the bfp valve is in the connection installed in the tank. Never knew the fact systems were routed inside the trailer. Now that is dumb.