Bighorn 3875FB Black Tank Flush

[teasac69]

Had my new 3875 FB about 3 months and used about 15 nights out. I'm curious how the black tank "flush" system works, i.e. are there spray heads mounted inside, overhead of the tank floor, etc. The reason I ask is I'm not exactly sure how to use it effectively and get a sure cleanout. I've done the washing, open the gate valve on my clear tube connector and watch for clear water. Then after we move, BEFORE the toilet is used again, I connect the hose and clear gate and find it draining more solid material???? Makes sense the road travel will loosen any left behind material but then why doesn't the flush system do that?

Am I flawed in my thinking that as long as the unit is level and I use the wash system for several minutes, I should be rinsing down all the solid material in the tank? I'm reluctant to leave the gatevalve closed and run the rinse for a while for fear of putting too much in the tank.

I'm only concerned for when I'm putting the trailer back in storage for a while that the tanks be super clean. I always drain the black tanks first and then use the gray tanks to push that material out of the line but it doesn't appear I'm getting it all out of the tank.

 

[danemayer]

Hi Tim,

When I first got our LM, I dumped the black tank while running the flush. I'd let it run clear for a few minutes and thought I was done.

Actually, I was closing the gate valve on toilet paper that hadn't washed out all the way. That paper got wedged in the gate valve causing a slow leak which led to multiple issues, particularly in the winter.

Now, after flushing for a few minutes, I close the twist-on gate valve that's at the sewer outlet and let the black flush run for 6 minutes (using my smart phone timer). Then I dump a 2nd time and lots more stuff comes out.

After running clear for a few minutes, I close the twist-on gate valve and run the flush for another 6 minutes. Then I dump a third time. The 3rd dump is usually pretty clear.

After that I close the black tank gate valve and run the flush for 75 seconds so there's a few gallons of water in the bottom of the tank.

I know a lot of people just dump the tank until it runs clear. But I've learned the hard way that on our rig, it takes multiple passes to ensure the tank is clean and there's nothing getting stuck in the gate valve.

Another thing is to use plenty of water when flushing. And minimize large wads of toilet paper.

 

[travelin2]

What Dan said. I have the after market twist-on plus use a clear elbow on our BH as well. It takes several flushes to clear the tank. In addition, if we're traveling and it's time to empty the black tank I do so upon arriving at our days destination. All that stuff has been sloshed around all day so any solids have been broken up and are in suspension. Don't need nearly as much water to flush the tank after dumping.

 

[branson4020]

Dan,

I seem to be following in your footsteps. I'm now at the point of having the leaky valve, almost certainly from tp smashed into the valve blade track. Do I have any hope of dissolving it out with some sort of in-tank treatment?

 

[danemayer]

Dan,

I seem to be following in your footsteps. I'm now at the point of having the leaky valve, almost certainly from tp smashed into the valve blade track. Do I have any hope of dissolving it out with some sort of in-tank treatment?

You can soften it by closing the twist-on gate and opening the black tank gate valve. I rinsed and rinsed and rinsed and also backwashed repeatedly. I also ran a long flexible shaft brush up through the sewer outlet to try and clean it (I think it was a dryer lint brush). Eventually it cleaned up.

 

[jbeletti]

Dan,

I seem to be following in your footsteps. I'm now at the point of having the leaky valve, almost certainly from tp smashed into the valve blade track. Do I have any hope of dissolving it out with some sort of in-tank treatment?

My guess... In order for tank treatment to really work on impacted TP in the valve blade track, you'd want to leave the valve fully open and have a sewer cap on or better, a gate valve at the end of the pipe as Dan suggests. In this manner, the chemical can be in better contact with the track. Maybe even empty the tank first, flush it well, cap the drain or add valve at the end, pull the black tank handle, add tank treatment through the commode, then about 5 gallons of water. You'll have water on both sides of the valve, thereby flooding the track and the treatment will be in a nice strong concentration.

This all said, I've never tried this but I sure might if I end up with a leaky valve again.

 

[teasac69]

Hi Tim,

When I first got our LM, I dumped the black tank while running the flush. I'd let it run clear for a few minutes and thought I was done.

Actually, I was closing the gate valve on toilet paper that hadn't washed out all the way. That paper got wedged in the gate valve causing a slow leak which led to multiple issues, particularly in the winter.

Now, after flushing for a few minutes, I close the twist-on gate valve that's at the sewer outlet and let the black flush run for 6 minutes (using my smart phone timer). Then I dump a 2nd time and lots more stuff comes out.

After running clear for a few minutes, I close the twist-on gate valve and run the flush for another 6 minutes. Then I dump a third time. The 3rd dump is usually pretty clear.

After that I close the black tank gate valve and run the flush for 75 seconds so there's a few gallons of water in the bottom of the tank.

I know a lot of people just dump the tank until it runs clear. But I've learned the hard way that on our rig, it takes multiple passes to ensure the tank is clean and there's nothing getting stuck in the gate valve.

Another thing is to use plenty of water when flushing. And minimize large wads of toilet paper.

Dan, always good to hear from one our most experienced members. I know you've been down whatever road we're talking about.

With our last 2-3 RV's, we made a decision to avoid putting paper in our sewer system. We purchased some of those very small step on lid cans and put one beside each toilet. We use those small plastic bags typically used for walking your dog and retrieving their leavings and put any "soiled" paper in one of them and drop it in that sealed can. I know this sounds a bit gross to most folks but trust me when I say we have had NO residual issues from it, i.e. smell, mess, etc., we also don't have to deal with all the paper issues that come along and we just simply dump those little cans daily to make sure they stay fresh. Those doggie poo bags work great to seal off any smell and house soiled tissue and we still put those in a seal can in the bathroom and our 1/2 bath in our BH. if anyone is interested, I can post some pictures of those little cans and you can pickup those doggie poo bags anywhere retail and they even sell them scented.

I do thank you for the feedback on the method and I'll try that for sure. thanks again.

 

[pcardoza]

Yes, GROSS is a terrific description. In all my years I've never had an issue with TP in the black tank. That's what it's for!

Dan, always good to hear from one our most experienced members. I know you've been down whatever road we're talking about.

With our last 2-3 RV's, we made a decision to avoid putting paper in our sewer system. We purchased some of those very small step on lid cans and put one beside each toilet. We use those small plastic bags typically used for walking your dog and retrieving their leavings and put any "soiled" paper in one of them and drop it in that sealed can. I know this sounds a bit gross to most folks but trust me when I say we have had NO residual issues from it, i.e. smell, mess, etc., we also don't have to deal with all the paper issues that come along and we just simply dump those little cans daily to make sure they stay fresh. Those doggie poo bags work great to seal off any smell and house soiled tissue and we still put those in a seal can in the bathroom and our 1/2 bath in our BH. if anyone is interested, I can post some pictures of those little cans and you can pickup those doggie poo bags anywhere retail and they even sell them scented.

I do thank you for the feedback on the method and I'll try that for sure. thanks again.