Black Tank flush port leaks at top of tank

FGoodyear · 08-03-2023, 04:31 AM

I have a 28-FRL-S fifth wheel camper There seems to be a leak on top of the black tank. I tried to use the flush port on the side of the camper and water and sewage from the top of the tank where I can't see where it coming from. Sort of like the line is not connected. Where does the flush line go into the black tank on this model and how do I fix this? I ended up using the flush port on my Flojet macerator pump. It did not shoot water out the top of the tank. Any ideas please.

**chuckster57** · 08-03-2023, 04:35 AM

Welcome to the forum

Black tank rinsers are usually mounted on the side of the tank not the top. If you’re getting water and sewage when using it, you may have a different issue.

Have you lowered the coroplast ( underbelly cover)? And then used the rinser to pinpoint the leak?

FGoodyear · 08-03-2023, 05:04 AM

Yes, I lowered the cover, at least the one covering and to the rear of the tank. The flush port looks like it goes in front of the tank. When I turn on the water it comes from over the top of the tank and sprays out on the back side. It was putting out sewage also. Closer to the drivers side

**chuckster57** · 08-03-2023, 06:06 AM

Is the toilet drain near the rinser? If so it may have come out. If not, then I think you’re going to be roving the tank. A cheap inspection camera would be a great tool to use to “watch” the top of the tank with the water running.

FGoodyear · 08-03-2023, 06:16 AM

Hmm... No the toilet is on the passenger side to the rear of the tank. The leak is more front or top side of the tank toward the drivers side. May have to pull the front cover down and have a look. Thanks for all your info. I'll post what I figure out

**chuckster57** · 08-03-2023, 06:20 AM

Did the tank ever get “over filled” I’m thinking it may have split at a seam.

FGoodyear · 08-03-2023, 06:44 AM

Not that I know of.... I've owned it about a year.

FGoodyear · 08-03-2023, 06:44 AM

The tank looks like its metal, but not sure

**chuckster57** · 08-03-2023, 06:59 AM

Can’t say I’ve seen many if any metal holding tanks. Post some pics please.

FGoodyear · 08-03-2023, 07:08 AM

Ok, I'll post some when I get home tonight

**flybouy** · 08-03-2023, 07:26 AM

Are you opening the drain valve when you use the rinser?

FGoodyear · 08-03-2023, 07:29 AM

Yes, checked that. Thought about that too, but not it. Thanks

**JRTJH** · 08-03-2023, 08:32 AM

Looking at the "clues":

Water AND SEWAGE leaking on top of the black tank.

If it's water and sewage, then it's not from the tank flush system. That nozzle is attached through the sidewall of the tank and pressurizing it would "leak clear water". If there's sewage "on top of the tank" it's from something other than the tank flush fitting.

If the tank valve is closed, you could pressurize the tank and push sewage up through a split or leaking black tank, but if the dump valve is open, the tank should NEVER fill with water, so a leak at the top could not occur.

All black tanks that I've seen in the past 30 years or so, have all been plastic. Either injection molded or roto-cast, but plastic. I'd suspect with the contents we put into the tanks, any "metal black tank" would corrode and start leaking at the seams within a very short time of using it on a regular basis.

I'd suspect your leak is either a "displaced vent stack pipe (many are just friction fitted into the black tank) or a leaking toilet base gasket or possibly a 3" toilet down pipe that's cracked and spilling the sewage onto the top of the black tank. Or, possibly, (hope not) you have a split black tank (probably on a top seam) that leaks when the tank is full or when towing and it "sloshes the contents inside the tank"....

But, using the black tank flush system with the dump valve open, it is "very difficult to impossible" to push sewage through the top or the top seams of the black tank because the tank simply never gets full enough to "leak upwards"....

Now, that said, if there is a loose flush nozzle fitting on the side of the tank, when the contents get high enough to cover the nozzle, you could have a sewage leak there and you're just "interpreting it as being when actively using the flush system" ??? <just guessing on that> ....

FGoodyear · 08-03-2023, 08:45 AM

Thanks. I will check out all suggestions. I appreciate the replies. Where its leaking from is towards the other end of the tank from the vent pipe and the toilet inlet. That's what has me confused because nothing at that end could be causing it. I'm at a loss.

Frank

**JRTJH** · 08-03-2023, 09:17 AM

Quote:

Originally Posted by FGoodyear

Thanks. I will check out all suggestions. I appreciate the replies. Where its leaking from is towards the other end of the tank from the vent pipe and the toilet inlet. That's what has me confused because nothing at that end could be causing it. I'm at a loss.

Frank

Remember that the black tank is only about 6-8" tall. Most are 56" long, 24" wide and fit between the frame rail brackets on the frame. Just being 2" off level can cause the "low end of the black tank" to be "half full with nothing to an inch or so of contents on the high end"..... That's one of the "confusing factors in interpreting tank status with a fully functional tank probe system"... Add in failing/false reading probes and determining the tank fill status gets really crazy.....

But, if your trailer is not "level side to side" then you could have 2 or 3 inches more "stuff on the low end of the tank"....

FGoodyear · 08-03-2023, 09:51 AM

Ok, thanks. I'll check that also

firestation12 · 08-04-2023, 07:09 AM

Quote:

Originally Posted by FGoodyear

I have a 28-FRL-S fifth wheel camper There seems to be a leak on top of the black tank. I tried to use the flush port on the side of the camper and water and sewage from the top of the tank where I can't see where it coming from. Sort of like the line is not connected. Where does the flush line go into the black tank on this model and how do I fix this? I ended up using the flush port on my Flojet macerator pump. It did not shoot water out the top of the tank. Any ideas please.

If finding time to repair whatever you will find as the cause, you might consider using a flexible rinser inserted through the toilet in the interim.

FGoodyear · 08-04-2023, 07:23 AM

good idea. I think its a crack in the top of the tank. Doesn't sound like an easy job

**chuckster57** · 08-04-2023, 07:31 AM

Quote:

Originally Posted by FGoodyear

good idea. I think its a crack in the top of the tank. Doesn't sound like an easy job

Its not easy but not real hard either. If you can get to the drain ther may be a molded part number on the tank so you can start looking for a replacement. I can attest to the LOW success rate of repairs after more than 10 years of working on these marvels.

FGoodyear · 08-04-2023, 07:36 AM

Yep, thanks. It will be a new tank for sure. Not going to try to repair it

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