Do you "fully" drain black and grey tanks?

[MILover]

We took our new 274DBH on its maiden voyage this past weekend. I'm happy to report that all went well and we really enjoyed it. We do have a question about emptying the tanks though:

At the dump station, we hooked up and proceeded to empty the black tank first (which had been about 2/3 full), followed by the grey tank. We have a clear elbow, so could see what was coming out. The thing is, after the initial rush of liquid from each tank, each would slow to a steady stream and continue to empty like that for several minutes.

So my question is, do you typically close the waste tank valves as soon as the initial gush of liquid slows, or do you wait for it to reduce to a trickle?

We stood there for several minutes, and it just kept draining and draining. I know it's good to have some fluid in the tanks anyway, so they don't dry out (I add more water and chemicals afterward), but it never did drain entirely while at the dump station. I should mention that the campground was empty and we had no line behind us, so it was a good day to putz around and experiment, but I know we want to target 10-15 minutes.

[NMWildcat]

We always try to empty fully and flush until clean. Then we put several gallons back in gray and black tanks. If time doesn't allow, then drain slightly past initial onslaught and close. Most tanks are bowed and will not fully drain anyway.

[Dave Lyon]

When I pull the black tank valve, I return to the bathroom and look down the toilet (mine is a straight pipe into the black tank) and when it has almost emptied I dump 5 gallons of water down the toilet to help flush it out.

After closing the valves, I dump another 5 gallons of water down the toilet with laundry soap/calgon and drive home. At home I flush it out again - by this time it's just soapy water. I add 5 gallons of water to both tanks and then store it until my next trip.

[5picker]

I've had two units like the OP's where not so much the black tank but the grey tank for sure, would trickle for 30 minutes. I just got used to after about 5 minutes of trickling, the valve went closed and we went on about our business to the next trip. Never had a problem.

No sense wasting any more time as a trickle isn't going to be bringing anything out with it anyway.

[gspot01]

I close 'em after a minute or two of trickling also. Doesn't hurt to leave a little bit of water in there. They'll never get completely clean and empty anyway, so I quit trying after a few times.

[MILover]

Originally Posted by 5picker

I've had two units like the OP's where not so much the black tank but the grey tank for sure, would trickle for 30 minutes. I just got used to after about 5 minutes of trickling, the valve went closed and we went on about our business to the next trip. Never had a problem.

No sense wasting any more time as a trickle isn't going to be bringing anything out with it anyway.

Good to know. I'm thinking we should try to hook up the flush hose while the black is emptying, then turn it on once the initial gush slows, just to put a little more force behind the remaining flow before we give up and open the grey tank valve.

Originally Posted by gspot01

I close 'em after a minute or two of trickling also. Doesn't hurt to leave a little bit of water in there. They'll never get completely clean and empty anyway, so I quit trying after a few times.

Glad to hear others have similar experiences. I figured we'd just need to stop after a point of "good enough."

[gspot01]

I should add, if you like the thought of a squeaky-clean tank, get one of the clear elbows with a hose connection flush valve on it. Works great!

[wnelsonfl]

Black tank first

[itat]

Originally Posted by gspot01

I should add, if you like the thought of a squeaky-clean tank, get one of the clear elbows with a hose connection flush valve on it. Works great!

Actually they don't work as well as you think. Check out this video for evidence and a comparison of tank flushing products and methods.

https://www.youtube.com/watch?v=dfTd0Slt_cU

[Dave Lyon]

Originally Posted by gspot01

I should add, if you like the thought of a squeaky-clean tank, get one of the clear elbows with a hose connection flush valve on it. Works great!

Most, if not all of Ontario Provincial Parks do not have a male fitting on the rinse hoses.......otherwise people would be flushing their tanks without any consideration of time and back up the line up of others.

[gspot01]

Originally Posted by itat

Actually they don't work as well as you think. Check out this video for evidence and a comparison of tank flushing products and methods.

Good video! Luckily I have a straight shot back into the tank, which is the most ideal situation. If I had an elbow like he's using, I probably wouldn't bother. Sure does feel good to squirt a bit of water back up in there after emptying though, even if its effectiveness is debatable.

[2Evil4U]

For me it depends if there are campers in line behind me. If no line, I'll dump black while running the flush, close it and leave the flush running while dumping gray, then finally dump the black again while still running the flush. Finally shut the flush off and let it drain as much as possible.

If there is a line I hook the flush and let it run while I attach the sewer hose, open the black valve, disconnect the flush hose, close black once its down to a trickle and dump gray.

Even if it completely stopped flowing there will always be more that comes out after the tow home from sloshing around.

In either case I will reflush the black when I get home and use my rolling tote to empty it into my septic system.

[m35a2]

I don't think I've ever used a dump station. Always stayed where there was a hookup.

[D_B Travelers]

I recommend the clear section also so you can see if "stuff" has cleared out of the black tank. I have the black tank washout hose connection and I do run it as soon as I open the black tank and leave it running until the flow is better. I noticed my gray tank is slower after the initial surge also, but wait until it really slows down before closing the valve.

[A32Deuce]

If Im level, both tanks seem to empty about the same. If nose down like at a dump station, then the black drains slower and not as complete as level. Gray really empties fast then.

[mkekflyers]

My Sunseekers both have pretty straight plumbing for both tanks. Dump the black first and, of course, "milk" the hose as it has a tendency at times to get an air pocket in it and stops flowing. Once I clear the hose, close the valve and dump the gray tank. If there's time, I run the black flush with the valve closed, contrary to the sticker, for a couple minutes, then shut it off and dump the black tank again. If I have plenty of time, I'll repeat it to try and clean the tank as much as possible. When that's all done, add a couple gallons water & tank chemical to the tanks, they seem to stay pretty fresh. I also use a spray bottle of Clorox bleach/water mixture to spray on all my hose ends and fittings to try and keep any contamination down. Even though I have completely separate fresh and gray water hoses, I might be a bit paranoid....

[sfsgm]

Originally Posted by NMWildcat

We always try to empty fully and flush until clean. Then we put several gallons back in gray and black tanks. If time doesn't allow, then drain slightly past initial onslaught and close. Most tanks are bowed and will not fully drain anyway.

Me, too.

[A32Deuce]

Full hookup site I do all I can to flush, dump sta. Dump and go!

[MoonStomper]

Great video!!!! Looks like the hose wand sprayer moved around down the toilet while using the Geomethod is the best way to go.

[mgarland48]

I've done the following and it seems to be working great.

Black tank dump til just a trickle. Shut off.
Start Gray tank dump til a trickle. Shut off.
Add about 1/2 a cup of Dawn liquid detergent to the toilet flushing a gallon or so while gray is draining.
After all is drained and valves shut, add about a 1/2 cup of Dawn to the Kitchen sink and follow up with a gallon maybe of water. Dawn helps break up grease in the gray tank.
Then drive away. The sloshing of the few gallons of water with Dawn in them will "splash" away crap and grease (so to speak).
This has worked very well and no smells either.