How To Replace RV Black Water Tank? Step By Step Guide

As an RV owner and avid DIYer, I value the freedom of home on the open road. But freedom comes with a responsibility to maintain complex systems like waste management. While no one wants to face the unpleasant realities lurking under the trailer, a cracked black water tank quickly turns dreams of adventure into a stinky nightmare. When I noticed a growing sewage smell from my beloved travel trailer, I knew it meant serious plumbing issues. After examining the underside and finding a visible crack in the black tank, I faced the messy task of replacing this vital waste system.

Black water tanks hold toilet sewage until it can be dumped at proper facilities. Cracks and leaks could leave me stranded with a major repair. I researched my options but determined the 10-year-old ABS plastic tank was too damaged to reliably patch. Facing an unpleasant but necessary project, I decided to take matters into my own hands rather than pay an RV technician thousands for the repair. After reviewing tutorials and gathering supplies, I was ready to tackle the removal and replacement on my own.

While daunting, I found the tank replacement empowering as it allowed me to fully renew this critical RV system myself. By sharing my experience, I hope to give other RV owners the confidence to take on manageable repairs and learn as they go. While messy and requiring patience, DIY tank replacement can save owners money and customize systems to their exact trailer. For those seeking RV knowledge and empowerment, my journey offers an opportunity to learn essential maintenance skills first-hand.

Facing the Dirty Challenge

Working under an RV is always a tight squeeze, made even more challenging when disconnecting sewage pipes and fittings caked with years of gunk. I started by locating the black tank’s outlet pipe connection at the tank valve. Expecting it to unscrew easily, I was frustrated when the plastic threaded fitting spun freely without disconnecting.

Apparently, the combination of vibrations and leaks from the cracked tank had broken the outlet fitting flange inside the tank. Some tar-like sewage ooze confirmed the leak and explained the smell that drove me to this repair in the first place. I’d need to cut the pipe to fully remove the tank.

After donning gloves and safety glasses, I used a rotary tool with a cutting wheel to cleanly sever the outlet pipe above the tank. Only then could I unscrew the broken flange inside the tank to fully separate the outlet plumbing?

The tank’s vent line was also stubborn, with corrosion fusing the threaded joint in place. Penetrating oil and heat from a hairdryer finally allowed me to disconnect the vent. Removing the sensor wires was easy by comparison, as was disconnecting the flexible toilet seal.

With all connections severed, it was time for the messy part – removing the tank itself.

Removing the Broken Tank

Having never replaced an RV holding tank before, I underestimated what a struggle it would be to wrestle the cracked beast out from under the trailer. After years of bouncing down the road, the tank’s mounting bolts had rusted in place, refusing to budge even after heavy soaking with penetrant. My ratchet only stripped the bolt heads. I ended up needing to cut them off with an angle grinder.

As I finally pried the old tank free, the remaining sewage inside sloshed out, turning an unpleasant job even messier. Once removed, I set up plastic sheeting and DIY splash guards to protect the driveway from more leaks. There was no denying it – I had grossly underestimated how much sewage remains inside a “drained” tank.

With the disgusting tank removed, I could inspect the interior condition. Removing the tank gate valve and unscrewing the sensor probes revealed corrosion and sludge buildup confirming that replacement was the right decision. The new tank would need some custom work to match the existing plumbing, but it was still the best option compared to patching the old tank.

Preparing and Installing the Replacement Tank

For convenience, I selected an ABS plastic tank to replace the old cracked unit. Matching the size and connections was straightforward thanks to standardized RV plumbing. I planned to reuse the existing tank valve rather than replace it.

The only custom work required was drilling new holes for the drain plumbing and tank sensor probes. Based on the measurements from the old tank, I marked and drilled connection points in the new tank for the drain outlet and vent lines. I used grommets around these holes to allow flex and prevent potential cracks from hard plastic edges.

After reinstalling the tank valve, I applied the plumber’s putty around the grommets and valve for an airtight seal. Tank sensors were installed with rubber seals, and I used sealant inside each sensor nut to prevent leaks. With the tank prepped, it was time for the messy installation under the trailer.

Plumbing the New Black Tank

To make the installation sanitary, I filled the new tank with water and dish soap, sealing the valve shut. This allowed me to thoroughly rinse any interior sludge during the first draining. I also installed a flexible “no-hub” drain connector, allowing the tank to be removed again in the future without cutting pipes.

With the tank ready, I secured it in place using new stainless mounting hardware less prone to rust. After reconnecting the drain outlet and vent lines, I added locking washers and PTFE thread seal tape at every joint for a watertight seal. All sensor wires were plugged back into their original locations after confirming a snug fit.

Knowing pipes and tanks can flex while driving, I fabricated an additional support bracket to prevent stress that could re-crack the tank. After a final check for any missed connections, it was time to test my work.

Testing for Leaks

With the cleaned tank reinstalled and plumbing reconnected, I added water to confirm no leaks before the true test – my first use of the toilet. Monitoring the tank gauges, I watched the water level rise as I added water. More importantly, no leaks appeared anywhere!

To complete the test, I flushed the toilet and drained the tank using the gate valve. Everything flowed as expected, with no leakage or odor around the new tank and connections. Satisfied with the results, my last step was reinstalling the trailer belly pan and insulation.

A Dirty Job Done Successfully

Completing this messy, smelly black tank replacement was hardly a glamorous DIY project. However, it saved me thousands of dollars compared to paying an RV technician. And after 10 years of service, my trailer has brand new plumbing ready for more adventures.

The project wasn’t quick or clean, especially wrestling out the rusty old tank caked in sewage. But with patience and the right tools, I was able to handle the custom work needed for this repair. While no one enjoys handling cracked sewer tanks, modern plastics make replacement relatively straightforward compared to patching.

For any RV owners facing a similar black tank repair, I strongly recommend replacement over attempting patch repairs. Follow safety precautions, allow plenty of time, and don’t be afraid to cut seized plumbing connections. And be sure to have a good cleanup plan ready! Though certainly unpleasant, tasks like this are very rewarding to complete yourself.

Now my trailer is ready to hit the road again, with one less worry thanks to its fresh new waste tank. It may only be a matter of time before the next RV repair project finds me, but that’s part of the adventure! For now, I can rest and recover from this stinky job well done.

Frequently Asked Questions

What are the signs that an RV black tank needs replacement?

Some common signs include visible cracks or leaks in the tank, persistent sewage odors, and blockages that reduce water flow. Tank sensors that display incorrect levels can also indicate issues. Any structural cracks or chronic odors likely mean a replacement is needed.

Can I repair a damaged black tank instead?

While patches or epoxy may temporarily repair small leaks, any structural cracks or failures require a full replacement. Attempted repairs often fail over time, while replacements provide reliable long-term performance.

How difficult is it to replace an RV holding tank?

Replacement difficulty varies by RV model and tank location. Tanks under the RV generally require removing paneling and working in tight spaces. Skill with plumbing, cutting, and sealants can make the job easier, though having a second person help is useful. Allow significant time for the project.

What special tools do I need?

Common tools include corded/battery rotary tools for cutting, wrenches for plumbing fittings, putty knives for sealants, and multipurpose cleaners/degreasers. Safety gear like eye protection, gloves, and masks is also essential.

Should I hire a professional?

While costly, hiring an experienced RV technician can be worthwhile if you aren’t comfortable handling sewage systems. They can also properly dispose of old tanks. However, DIY tank replacement can save thousands of dollars.