Backflush the black tank

[Greg C.]

If you have a shutoff valve at the end of your sewer line have you tried back flushing your black tank allowing water from your gray tanks to back up into the black tank and then opening the shut off valve and letting the water that backed up into the black tank to run out? This would be done after emptying the black tank. I read on another site that this works well for getting any remaining waste out of your black tank after draining it.

[Jim & Mary]

I don't think I understood a single thing about this post. Could you please try to clarify?

[r time soon]

Why would one want to use grey water to rinse out your black tank? Isn't that why there is a black tank flush water connection in the docking station? Use that to rinse and spray the inside of your black tank after emptying.

[mhs4771]

I fill my Black tank with 30 Gal of water using the Black Tank Flusher at least 3 times, letting it drain before refilling. The Gray tanks get dumped last after I'm finished with the Black.

[hoosierguy]

Originally Posted by mhs4771

I fill my Black tank with 30 Gal of water using the Black Tank Flusher at least 3 times, letting it drain before refilling. The Gray tanks get dumped last after I'm finished with the Black.

That is exactly what I have been doing for 7 years and it has worked well for me.

[travelin' texans]

Originally Posted by Greg C.

If you have a shutoff valve at the end of your sewer line have you tried back flushing your black tank allowing water from your gray tanks to back up into the black tank and then opening the shut off valve and letting the water that backed up into the black tank to run out? This would be done after emptying the black tank. I read on another site that this works well for getting any remaining waste out of your black tank after draining it.

Technically then you have 3 black tanks.
Not sure about your particular RW, but with mine if the bath grey tank overfilled it would back up into the shower, some times while showering, personally would rather be standing in dirty shower water instead of black water.
Also in the past have been to places that allowed grey water to be drained on the ground to water plants, once you've combined the grey & black that would no longer be possible.
So my simple answer to your question is "NO" I have not done this nor would I ever want to.

[mhs4771]

Typical procedure for dumping tanks:
Drain and flush the black tank(s), how you actually do it is up to you as everyone has their own way.
Once done and Black valve(s) are closed now open and drain Grays, usually two. This will rinse out the sewer lines both under the RW and the line to the CG sewer connection with the Gray Water. Then close or leave open, your choice, I close mine to prevent any creepy crawlies coming up into the RW via drain lines.

[Greg C.]

I saw this posted on another site and was just wondering if any of you had thought about it. I don't have a shut off at the end of my line since I have the wastemaster system so I will probably not be trying this also. I have always used my black tank rinse and will continue to do it this way. One more question do any of you with the shut off leave both gray tanks open to double your capacity? Thanks for your replies.

[hoosierguy]

Originally Posted by Greg C.

I saw this posted on another site and was just wondering if any of you had thought about it. I don't have a shut off at the end of my line since I have the wastemaster system so I will probably not be trying this also. I have always used my black tank rinse and will continue to do it this way. One more question do any of you with the shut off leave both gray tanks open to double your capacity? Thanks for your replies.

After dumping the black tank and using black tank flushing system 3 times (refilling black to approx. 30 gals.), I then dump gray tanks. I have the added gate valve at the dump outlet. I close the external gate valve, I close the black tank gate valve and open both gray tank gate valves. This allows the two gray tanks to equalize.

When we are staying in our coach full time, we can go 8 to 10 days before needing to dump tanks, although, I generally dump the tanks every 7 days. This has worked well for us over the past 7 to 8 years.

[mhs4771]

The equalize trick between Gray tanks does not work for all floor plans. To work both Grays must be at the same level, with our MB floor plans it won't work because the gray is in the drop down section next to the Black, while our galley is up in the belly above the axles. If we were to leave both open, water from the galley would flow into the gray filling it up and leaving the galley tank empty.

[Elliott & Vicky]

If you back flush the black tank with one of your gray tanks, you will get a bigger surge of water at once,far more than the black water flush can give you. It will loosen up things that simply using the back tank flush can do.

[inb2winger]

Have been back flushing with the grey tank since 2006 and it works better than the back flushing with the installed black tank flush hook-up. Usually do it three times if the grey tank is full. Just make sure you shut they grey tank after about 30 to 45 seconds so it does not equalize back into the grey tank. then open the final flush valve to empty the black tank, repeat until the grey tank is empty.

[RomanyLife]

Originally Posted by mhs4771

The equalize trick between Gray tanks does not work for all floor plans. To work both Grays must be at the same level, with our MB floor plans it won't work because the gray is in the drop down section next to the Black, while our galley is up in the belly above the axles. If we were to leave both open, water from the galley would flow into the gray filling it up and leaving the galley tank empty.

HI M & A;
I can see how you might think this is so, but you are incorrect. The tanks will both fill because it is a closed system, not two open tanks. The tanks will both fill, first one, and then the other through backflowing up to the other one. Our grey tanks are actually plumbed together (and they are at different levels), we only have ONE dump valve, and it works BRILLIANTLY. We love it, and use the Wastemaster system. It's genius.

[Shane Wood]

Originally Posted by Greg C.

I saw this posted on another site and was just wondering if any of you had thought about it. I don't have a shut off at the end of my line since I have the wastemaster system so I will probably not be trying this also. I have always used my black tank rinse and will continue to do it this way. One more question do any of you with the shut off leave both gray tanks open to double your capacity? Thanks for your replies.

When I got the wastemaster system I purchased the adapter so I could attach it to the twist lock fitting. I did not cut it off and glue the cam lock fitting on the pipe. This gives me other options if the wastemaster springs a leak