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Topic: Flushing Black water tank (Read 1231 times) previous topic - next topic

Flushing Black water tank

Hello all, I have a ?, How do you all flush out your black water tank. On my Eagle I had a flush valve that I could hook up to and flush out the tank once I dumped, I looked in the old post and read talk of a third valve. Not sure what that might be. Any insight would be great. We have a 92 U300 40'. Thanks in advance  Andy
Andy & Eileen
MONTROSE COLORADO
1992 U300  40' 6V92 TA
2016 4 Runner
1998 Jeep Grand cherokee

1998 Jeep Grand Cherokee) Build # 4135 Skp# 122921

Re: Flushing Black water tank

Reply #1 –
@Andy black water flush was not standard on the 92's. I installed an aftermarket one on mine. No-Fuss Flush - Lakeview 336A - Sewer Flushing - Camping World

I also installed a third valve. I'd advise to install both.

The advantage of the third valve is that you can use the gray water to back wash the black tank after you've emptied it. Here is a thread where the third valve is discussed in detail. Grey and Black water valves and here is a link to a picture of my setup in the same thread. Grey and Black water valves.

The procedure is to wait till the gray water tank is almost full then dump the black tank. Then close all the valves. Open the gray water valve then open the black water valve. The gray water will now equalize with the black tank back flushing the tank stirring up the sediment in the bottom of the black water tank. The gray water has detergent from the kitchen sink and shower so will help to scrub out the black tank. Now close the gray water valve and open the third valve emptying the black tank. You will be amazed at how much crap (sorry no pun intended :) ) comes out. Be sure you have a clear section in the waste line so you can see what is coming out. You can do this several times. Once the black tank is running clean I usually do one last rinse of the black tank leaving about 5 to 10 gallons of water in the black tank. That way any new solids introduced to the black tank will be covered with soapy water reducing any odors. Now open the third valve and the gray valve to finish the dump. Not as complicated as it sounds once you've done it a couple of times.

The advantage of the black water flush is that occasionally you can do a gray tank flush by filling the black tank with fresh water via the flush and run it back through the gray water tank. The first time I did this a ton of crap came out of the gray tank. Probably 20 years worth of crap! :)

see ya
ken
The selected media item is not currently available.ken & dori hathaway & Big Agnes
🍺1992 U300 GrandVilla WTBI #4150 FOT FBP 2011
✨6V-92TA DDEC Parlor Coach 350HP Series 92
🏁2011 Nissan XTerra Pro-4X

Re: Flushing Black water tank

Reply #2 –
I have a black valve and a gray valve.  Those each flow thru a single third valve that I added.

I open the third, then the black valve and drain the black tank.  I close the third valve, the black valve is still open and then I open the gray valve for just a moment or two, letting gray water flow up into the black tank

I close the gray after a moment, then open the third valve back up, and then the  black valve open again to let the flushing water from the black flow out.

Then close the black valve and open the gray valve to drain the gray tank......

whew.....seems complicated when I put all the steps in, hope I got it right, think it through as you do it, think the idea should be apparent.....using some gray water to clean a bit the black tank.

There are other ways, but this is the third valve method Andy that I use.

Mike
Mike
2001 U320 4010 Build 5878 (Gus)
Wrangle Unlimited Toad
Nacogdoches

Re: Flushing Black water tank

Reply #3 –
Andy,

Here is photo of the 3rd valve you are reading about.  On my '93 U280 it was pretty simple to install - your setup may be different.  In the photo, the 2 valves with the horizontal open/close handles are in the original factory installed position.  The new (added) 3rd valve is the one with the vertical handle.  A additional advantage to having a 3rd valve is it acts as a "safety backup".  If one of your factory valves malfunctions/jams/leaks, you just use the 3rd valve to "hold the load" until you can get around to making repairs.

If you don't want to permanently install a 3rd valve, they make a number of different "temporary" flush valves that you hook up when you are dumping, then remove.  Check out the online catalogs for many options:

Flush King - Valterra FK-01 - Sewer Flushing - Camping World
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Flushing Black water tank

Reply #4 –
I put on the third valve the first time on my 99 in 2001.  I have had one on each coach since and do as Mike said. Works great.
2025 Wanderbox Outpost 32 on F600 Expedition Motorhome
2015 Born Free Royal Splendor on Ford 550 nonslide version  for sale
Former Coaches  covering. 360,000 miles
1999 34 U270
2000 36 U320
2001 42' double slide U320
2018 Jeep Rubicon

Re: Flushing Black water tank

Reply #5 –
So did my '89 come standard with the 3rd valve and FT stopped producing, or am I the beneficiary of a previous owners' mod?
Jay
1989 U280 SE, 36', 3208T Cat, build 3292

Re: Flushing Black water tank

Reply #6 –
@Jay As far as I know FOT never installed a third valve. You are probably the beneficiary of your PO.

see ya
ken
The selected media item is not currently available.ken & dori hathaway & Big Agnes
🍺1992 U300 GrandVilla WTBI #4150 FOT FBP 2011
✨6V-92TA DDEC Parlor Coach 350HP Series 92
🏁2011 Nissan XTerra Pro-4X

Re: Flushing Black water tank

Reply #7 –
I added the third valve earlier this year. The hardest part was cutting off the old Thedford fitting, and it wasn't all that difficult. Adding a black water tank flush is on the list.

Re: Flushing Black water tank

Reply #8 –
I don't have a third valve on my 91 GV,  I just flush the black tank after dumping it using the flush valve and I leave the black valve open.  I dump the gray tank and shut the black valve after some back flow into the black tank.  It is a matter of judgement as to when to shut the black valve.  I usually dump the gray tank after it hits 3/4 full so I have plenty of gray water to flush into the black tank.  Have a great day  ----  Fritz
Fritz & Kathy Johnson
1991 36'

Re: Flushing Black water tank

Reply #9 –
When I went to buy a third valve (the kind that hooks on the existing lugs) the service manager told me they always put one of these on any RV that leaks--cheaper than dismantling the existing system.
So if you are looking at purchasing a RV and it has one of these valves it might be because the gray or black water valves leak or the PO was a savvy camper.
Nitehawk,  Demolition Lady, & our NEW master, Zippy the speeding BB cat.
1989 Grand Villa 36' ORED
Oshkosh chassis, 8.2 DD V8
2006 Saturn Vue AWD

Re: Flushing Black water tank

Reply #10 –
I carry a removable 3rd valve, can either back flush or deal with a bad black or grey valve after my trip when I get home.
Dave Cobb
Buckhorn Lake Resort The Club, #6202, Kerrville TX
check the map.  I do rent it out when I am traveling!
2001, U320, 36' #5887, in Kerrville, FT Club #17006, (7/23 to present)
2024 Jeep Grand Cherokee L, Summit, white
EX: 98 U295, 36' #5219, (mid door), (4/13-10/23)
EX: 93 U225, 36' (4/11 to 4/13)

Re: Flushing Black water tank

Reply #11 –
Quote from: Michael & Jackie –
I open the third, then the black valve and drain the black tank.  I close the third valve, the black valve is still open and then I open the gray valve for just a moment or two, letting gray water flow up into the black tank

I close the gray after a moment, then open the third valve back up, and then the  black valve open again to let the flushing water from the black flow out.

Then close the black valve and open the gray valve to drain the gray tank......
That is exactly the method I use.  I will open/close the grey valve several times in the process, flushing the black tank 3-5 times until it looks like most everything is gone.  Then I close the black and drain any leftover grey water.  This summer trip is the first time I have been out since installing the third valve and it works great!  Altho I do have a tank-flush on the 2002, this is simpler and I don't have to hook up the second hose to the flush fitting.  I love this plan.  Tank readings are better, too!
The selected media item is not currently available.Brad & Christine Slaughter
Was:  1990 U280 36'
Was:  2002 U270 36' (With a bathroom door) Build #5981
Is:  2021 Leisure Travel Van Wonder 24RL
2015 Jeep JKU, 2003 S10 QC 4x4 or 2017 C-Max
Lake Havasu City, AZ (or Gillette, WY)

Re: Flushing Black water tank

Reply #12 –
On ours, we dump the black in the normal fashion, then pour a couple of buckets of water in the toilet and dump the black again. This results in clear water coming through the pipe. Then we dump the gray which flushes the hose. We finish off by adding Dawn and water softener to a bucket of water and pour that down the toilet.

I don't see the need for back flushing nor for a third valve (except in the case of a leaky valve) Nor do I see the need for any additives as the tanks are ventilated and no odor should enter the living area if those vents are operating as they should. I had to remove the black tank on this rig as it was leaking. That gave me an opportunity to examine it closely. Clean as a whistle.

This topic is kind of like tires pressures - lots of impassioned opinions.
jor
93 225
95 300
97 270
99 320

Re: Flushing Black water tank

Reply #13 –
Thanks all for the information, looks like I have some reading to do.
Andy & Eileen
MONTROSE COLORADO
1992 U300  40' 6V92 TA
2016 4 Runner
1998 Jeep Grand cherokee

1998 Jeep Grand Cherokee) Build # 4135 Skp# 122921

Re: Flushing Black water tank

Reply #14 –

I only have the two valves, Black and Grey,

Easiest way to dump the Black tank, Is make sure there is plenty of water in it before dumping,

Then after a Long drive, Dump it immediately, The long drive keeps it all sloshing around and should break free any Solid buildups, 

Dump the Black tank, close the Valve, Open the Grey tank, That flushes out the dump hose, Close the grey tank,

Put your hose back in the tube thats on the angle, That drains the Hose,  Its simple, Clean, and easy,

I dont see a need for flushing the Black Tank, If it wont flow out freely, The black tank, You dont have enough water in it,
 
Mine runs out like water, I dont have smells from the Black or Grey tanks, But I do pour a quarter cup of detergent down the Toilet, Before I leave home when its empty,

I dont even wear gloves, Its that easy and clean to do,

Make sure all  your Hose connections are very tite before you open any valves, If you dont, Then you will need gloves,
Cheers,
Brian,

Toys, 1989 Grand Villa, 36 foot, ORED with 300 Hp Cat. 2002 Gemini 34 foot Sailing Catamaran, 2006 Honda Super Blackbird 1100XX, 2002 ZR7 750 Kawasaki,
25 HP Chinese tractor and Backhoe,

Re: Flushing Black water tank

Reply #15 –
I installed the third valve and use it to facilitate using grey water to clean the black tank. You can accomplish just about the same task by raising the hose and doing the "grey valve shuffle." You may need a helper.

I've been pleased with the utility of the third valve. I use a Polychute hose system that include sight glasses. I can see how the effluent from the black tank clears very well by the third back flush from the grey water tank.
J D Stevens
1997 U295 CAI 36' Build #5085
2002 Subaru Outback
Motorcade 16869
Bellville, TX

Re: Flushing Black water tank

Reply #16 –
Either MOT of FT can do it fine. 
2025 Wanderbox Outpost 32 on F600 Expedition Motorhome
2015 Born Free Royal Splendor on Ford 550 nonslide version  for sale
Former Coaches  covering. 360,000 miles
1999 34 U270
2000 36 U320
2001 42' double slide U320
2018 Jeep Rubicon

Re: Flushing Black water tank

Reply #17 –
I added a black and grey water flush to my 98 u295 fot installed the third valve for me all parts are on amazon or at camping world

Re: Flushing Black water tank

Reply #18 –
Here's what I do: when leaving campground...empty black tank, close valve then flush toilet for about five minutes while city water still hooked up so as to not deplete your fresh tank...unless you want to drain some of the fresh water (some folks don't like to drive with much water but I need as much weight forward as I can get for better handling).  Throw in a bag or two of ice.  Hit the road.  Immediately upon reconnecting sewer at next campground...drain black tank.  Tank level monitors will then be accurate again for a time. 
Dwayne Keith
1992 U240
3116/MD3060