How to really empty your black tank

[Bill Johnson]

Originally Posted by Scottenj

It’s not a sensor problem but I did recently add the Sea Level Systems tank monitors because I want more accurate readings of the tank level.

That's the one I saw

[JFlightRisk]

Originally Posted by Scottenj

It’s not a sensor problem, the tank just doesn’t empty all the way. I drain it, it still reads 1/3 full and the bottom of the tank is bulging down from the retained liquid. If I raise the nose of the camper all the way and press up on the tank I get 20 plus gallons out after previously draining it.

Agreed. Not only do the sensors have to work, but it's necessary the tank does what it's suppose to, and drain completely. I'm curious why there's tanks sagging now. Perhaps Jayco's using a different brand of tank in production?

Ours were made by a company called AmeriKart. per the label stuck to them.

[Scottenj]

Originally Posted by Bill Johnson

That's the one I saw

I put a 40 gallon water tank into a utility trailer back in 2010 and put that sensor system on the tank and it has been great. Last weekend I put them on all four tanks in my camper. No more 1/3, 2/3, now it is 5%, 6%, etc.

[Scottenj]

Originally Posted by JFlightRisk

Agreed. Not only do the sensors have to work, but it's necessary the tank does what it's suppose to, and drain completely. I'm curious why there's tanks sagging now. Perhaps Jayco's using a different brand of tank in production?

Ours were made by a company called AmeriKart. per the label stuck to them.

Have you checked the two tanks under the basement when they are full, my understanding is sagging is pretty standard in fifth wheels.

When you drain your black tank does it read empty or always read 1/3 full because that is also common in fifth wheels because of the sagging.

[Magnolia Tom]

Here’s a suggestion. If you plan on using plywood to support the tank, why not add some shims or extra supports at the rear of the tank so that it’s sloped to the drain? Second suggestion would be to use some exterior grade or marine plywood and not just regular plywood or OSB.

[Scottenj]

Originally Posted by Magnolia Tom

Here’s a suggestion. If you plan on using plywood to support the tank, why not add some shims or extra supports at the rear of the tank so that it’s sloped to the drain? Second suggestion would be to use some exterior grade or marine plywood and not just regular plywood or OSB.

It is already somewhat sloped and there is very little space to work with. I am putting in 3/8" exterior grade plywood and that will be tight. In fact I am a little worried even with that. The tank is supported around the top edge and then underneath and I think adding the plywood will lift the tank off the top supports and transfer all the weight to the bottom cross bars.

What I plan to do it glue and screw oak strips to the underside of the plywood in between the steel cross bars to stiffen it. I will post some pictures once it is done, hopefully this weekend.

[Bill Johnson]

Originally Posted by Scottenj

Have you checked the two tanks under the basement when they are full, my understanding is sagging is pretty standard in fifth wheels.

When you drain your black tank does it read empty or always read 1/3 full because that is also common in fifth wheels because of the sagging.

What if you raise the brackets 3/8 on the ends so the plywood would fit. This would lower the square tubing 3/8

[Scottenj]

Originally Posted by Bill Johnson

What if you raise the brackets 3/8 on the ends so the plywood would fit. This would lower the square tubing 3/8

What brackets?

There are 2 - 12" I beams that run the length of the camper and the 2 cross braces are bolted directly to the bottom of the I beams. One of the cross braces is square tubing and one is kind of a C channel.

I might put spacers between the cross pieces and the I beams, maybe something like 1/4" spacers. I need to make sure the Coroplast still fits. The tanks are constrained in every direction so I am kind of trying to thread a needle.

[Bill Johnson]

The two cross braces that are screwed to the 12" beam raise the part that screws into the 12" beams by welding or like you said put a 3/8 block in between that would give you room for your plywood

[Scottenj]

I built the black tank support today and part of the gray tank support. I plan to finish and install them tomorrow, pictures to come.

Another Jayco workmanship issue I found today is there is a partial saw cut into the black tank near the very front. I will reenforce that before I close it up.

[Scottenj]

The tanks supports are built and installed and the tanks no longer bulge and drain completely with the trailer level.

Here is the original situation, this shows the two cross bars under the tanks. The tanks are empty in this picture, normally the tanks bulge between the front and the first bar, the first and second bar and the second bar and end.



Here is the support I built, it is 3/8" exterior grade plywood with oak 1x2 support, the oak is screwed to the plywood with lots of counter sunk screws and glued as well. The left side in the picture will get screwed to the frame in front with tek screws (that will be the high point), the two channels are where the cross supports will go and the right end has 1x2 sticking off the end for support straps. The 3/8" plywood goes over the support beams and I was concerned about pushing up the tank too much because there is a lip on top that currently carries a lot of the weight. I put 1/4" spacers between the I beams and cross members so the plywood only presses up 1/8". I had to be careful I didn't lower the cross beams too much and create problems with getting the bottom cover back on.



Here is the tank support in place looking towards the front of the camper.



Here is the back of the support installed showing the support straps.



The tanks now slopes smoothly down from front to back with a flat bottom (no bulging at all), more importantly between the tank support and re-plumbing the outlets the tanks now drains completely with the camper level.

[JFlightRisk]

Originally Posted by Scottenj

Have you checked the two tanks under the basement when they are full, my understanding is sagging is pretty standard in fifth wheels.

When you drain your black tank does it read empty or always read 1/3 full because that is also common in fifth wheels because of the sagging.

I have looked at them when they were almost full, after reading some of the posts here, and being the curious type. Not much, if any bulging. We have a small-ish TT with 32 gallon tanks, but they are held up by the tank flange with aluminum plates screwed to the floor. There are no cross braces on either one. The black has always read empty, and the gray needed the sensors replaced. It started to read 1/3 after dumping, so I replaced the sensors with the Horst brand.

Perhaps our tanks are small enough so they don't bulge at the bottom.

[Scottenj]

In case anyone ever needs to re-plumb their tanks.

The drain lines are 3" Drain Waste Vent (DWV) ABS, DWV is designed for drain lines that aren't under pressure. The pipe and fittings are glued together, I originally assumed they were PVC but they aren't and you can't glue PVC and ABS together. Lowes actually sells the pipe and fittings but has limited availability in stores, you can order it on-line from them.

The 3" lines attach to the tanks with hose clamps and lots of white sticky caulking. I tried to find out what Jayco used but ran out of time. My dealer said to use Butyl tape and I did and I have no leaks but Jayco later got back to me and said they use Quad sealant.

I believe the tanks themselves are Polyethylene, I know the ICAN H3554 50 gallon Jayco replacement tank is Polyethylene.

[Scottenj]

Originally Posted by JFlightRisk

I have looked at them when they were almost full, after reading some of the posts here, and being the curious type. Not much, if any bulging. We have a small-ish TT with 32 gallon tanks, but they are held up by the tank flange with aluminum plates screwed to the floor. There are no cross braces on either one. The black has always read empty, and the gray needed the sensors replaced. It started to read 1/3 after dumping, so I replaced the sensors with the Horst brand.

Perhaps our tanks are small enough so they don't bulge at the bottom.

I have the two 50 gallons under the basement and they both bulge although the black bulges more than the gray. I think the black bulges more because the black sits full more often, for example on hook ups the black valve is closed and gray valves are open.

I also have a 35 gallon tank for the galley and have no problem with that tank so I think you are right that the smaller size is the difference. I also think travel trailer tanks may not be as shallow as the tanks under the fifth wheel basement.

I read over the weekend that Luxe puts 5/8" plywood under all their holding tanks. I would bet every fifth wheel owner without plywood under the 50 gallon tanks under the basement has at least some bowing and some retention of liquids. I know other Jayco owners who after the first trip never saw the 1/3 full light go out on their black tank ever again. There is also another post earlier in this thread about how Montana mentions the need to elevate the front of their rigs to empty the tanks in a factory walk through video so I think this is a common problem with the big tanks.

[jpgale]

Dragging up an old thread here, I got a 2022 355mbqs, and I am noticing some of the same issues as in this thread. I am not convinced the black tanks are draining well, and I have the light on all the time. It is a shame I can not see the pictures as I think supporting the bottom of the tanks sounds like a good approach. I am also seeing a lot of air pressure in the black tank when using the flush to fill it up as I get to about 30 or so gallons if I open the valve it will spit the water back up and when I hit 40 gallons today it was forcing air past the seal and bubbling, this is not a problem when the tank is empty. I was thinking my vent maybe blocked but I am wondering if I have a pyramid and the tank is not getting drained. I will be going back to the trailer on Tuesday so will take my endoscope and put it down the toilet to take a closer look. I would see the outlet being angled up as the outlet where I connect the sewer hose was like that and I just fixed it (did help the flow) I would ask the dealer but they will keep it forever and not actually fix the problem I am asking about (they did that with the obviously flowing up end pipe. I was planning on putting in electric drain master valves and see level guages over the winter so I will just make sure I have a selection of 3 inch pipe and fittings to rebuild that part as well.

I don't suppose the OP still has the pictures the he could send me that would be super helpful.

[Scottenj]

The tank redo starts on page 28 of the document here: https://scottenjones.com/wp-content/...l-Upgrades.pdf

If I get the time at some point I will update the document because I have made a lot of other changes since I wrote it but the waste tank modifications are still the same.

[JB13502]

Originally Posted by Scottenj

The tank redo starts on page 28 of the document here: https://scottenjones.com/wp-content/...l-Upgrades.pdf

If I get the time at some point I will update the document because I have made a lot of other changes since I wrote it but the waste tank modifications are still the same.

Wow! Quite the write up, thank you for sharing. My 377RLBH is pretty much the 355's big brother. I've only briefly scanned it and think that I will found quite a few useful tidbits here. Again, thanks.

[jpgale]

Originally Posted by Scottenj

The tank redo starts on page 28 of the document here: https://scottenjones.com/wp-content/...l-Upgrades.pdf

If I get the time at some point I will update the document because I have made a lot of other changes since I wrote it but the waste tank modifications are still the same.

Thanks this is an awesome document that looks like it has other interesting things in it. When I get around to doing the work towards the end of the year I will post pictures of what I find and do on here as well.

[camjam]

Originally Posted by Scottenj

You have to unhook to do it.

Glad I am not in line behind you. lol

[jimmoore13]

Originally Posted by jpgale

<<SNIP>> I am also seeing a lot of air pressure in the black tank when using the flush to fill it up as I get to about 30 or so gallons if I open the valve it will spit the water back up and when I hit 40 gallons today it was forcing air past the seal and bubbling, this is not a problem when the tank is empty. <<SNIP>>

Your through-the-roof sewer vent should relieve air pressure in the black tank.
If you have water coming past the flush valve, you've added too much water.
The OP's demo included a device for measuring water input to the black tank from the dump connector.
I don't believe the OP recommended adding the tank's full capacity...as in adding 50 gallons to a claimed 50 gallon tank.

PS. I may be confusing this thread with another thread. :-)