Waste water piping configurtion

[DaveGoodman]

We just purchased a 2014 Model 3735 MK. Dealer told us to drain the black water tank first, then the grey water and lastly the galley. He said to leave all of the valves open until everything drains out. Then to close the valves in reverse order. Do these tanks drain through each other?

We have been full timing for a few weeks and the clear elbow shows clear water flowing as we near the finish of this process. Everything I read on the forum indicates that I should be back flushing the black water tank somehow and closing the valves after each tank draining. Open for suggestions.

[AZ Traveler]

Dave,

Welcome to the forum!

The tanks do not drain through each other but when you have multiple valves open they can back fill a tank at a lower level. The advice you got from the dealer is pretty solid. Flushing the black with the rinse system is good to do occasionally but is not needed every time you dump. I tend to rinse it well when it is not going to get used for awhile.

The only level indicator that tends to work reliably is the fresh water. You will find you really don't need indicators on the other tanks. Dump black every 7 days or so and the grey dump when they are full and backing up in the shower or sink.

[DaveGoodman]

Thanks for the response, One other question. Do I need to purchase a rinse system? If so which one would you suggest?

[rames14]

I know that my 2015 has a black water rinse in the control panel (convenience center). I can’t remember which year they added the convenience center. If you have an area with Winterizing valves, water heater bypass, dump valves you should have an inlet for black water rinse. As Zack said, the dealer gave you good advice. We always keep our valves closed until dumping, then dump black first, close it then dump gray and galley. Best of luck.

[DutchmenSport]

The advise you received is very sound and the practice we all do. Dump black first, then the grey tank (or tanks if you have more than 1). The cleaner water flushes out the dirtier water from the hose so you are not storing your hoses with a bunch of "nasties" in it.

About back-flushing. I back flush my shower/bathroom sink into my black tank (toilet) every time I dump. I automatically attach a 3rd valve to the outlet, like a Flush King, but is a knock-off brand I've had for over 20 years.

The idea is to dump your black tank completely first. Then close off the flush king valve and open the grey tank. The grey tank will back-flush into the black tank. After a few seconds, the tanks will equalize. I usually count to 10. Then you shut off the grey valve and open the flush king. This will now dump the black tank again. Keep repeating this until there is almost no water left in the grey tank, then use the last remaining water in the grey tank to flush the hose out.

When you do this, youi'll be amazed how much more toilet paper and "cruddies" flush out the second, third, even the 4th time (if you have enough water left). The flush king type valve has a clear section you can see what's coming out. Once you've seen how much more flushes out, you'll be doing the back flush every time too.

I dump my tanks every 2 days. Why? Because we camp, usually where we do not have full hooks ups. (no sewer, but only a dump station). I have a 32 gallon Barker Blue Tote to haul my waste water to the dump station so we don't have to break camp to dump. I have learned over the last 20 years, that if we dump the black every 2 days, and back flush the grey, it's just about perfect to fill the Blue Tote without over spilling.

They say, you should dump your black tank only when it is full. I have found that is not true.... IF you backflush and backflush every time. But the biggest reason I started doing it this way, years and years ago, was so I would not over spill my Blue Tote.

[Mikendebbie]

The 2014 brochure shows a convenience center (screen shot below). This is where you would find connections to the black tank rinse and the tank valves.

[rohrmann]

I actually dump the galley tank second and then the grey tank from the shower and bath last. The galley tank waste water can be almost as nasty as the black tank at times with food particles and some grease added to the mix.

[DQDick]

I start the black tank flush when I open the black tank and leave it on. Once the black tank is drained and all that is coming out is water from the flush then I open both the grey tanks at once, that plus the water coming in from the flush tends to flood the black tank again. Once it goes down to the flush flow again then shut off the flush and once the flow stops close the black tank. You'd be surprise how much comes out after the flood of grey water. Before that the flush is running clear so it does get some things that are probably stuck to the tank walls.

[Rondo]

Each person has their own way of dumping tanks. Some leave their gray tanks open till about two day before dumping the black tank the close them and use them to rinse the "slinky" of any solids that might have settled in the grooves of the slinky. Some leave their tanks closed all the time until dumping. NEVER LEAVE YOUR BLACK TANK OPEN WHILE SITTING AT A CAMPSITE! You will develop a "pyramid" in your black tank of solids and all of the liquid drains out creating that pyramid. Once formed that pyramid is quite hard to get rid of. I dump about every 4-5 days and leave all my drain valves closed. You should have a black tank flush in your convenient center so hook a second hose up to that to help flush the black tank when dumping. I do as DQ Dick and turn my flush on when opening the black tank valve. After it is drained I close the valve and let the flush run into the tank for about 5 minutes then open the valve again and empty the tank. I then close the black tank valve and open the galley valve and dump it and like Bob this takes out any possible debris in that tank and then close that valve. Finally, I open the shower gray tank valve and use that to rinse any solids from the slinky. When done, I go inside and fill the toilet and dump it about four or five times giving the black tank some water for the solids to break down in. I do use a black tank additive (Happy Camper) and this helps to break down the solids even more.