How to Repair an RV Black Tank

by Lynda Altman
RV black tanks can get damaged by road debris.

RV black tanks can get damaged by road debris.

Cracked or damaged black tanks in an RV are not only messy, but they pose a health hazard. The black tank is usually reserved for blackwater--waste water containing human waste. It is important to repair the leak quickly. Left unchecked, the tank can rupture. Ruptured tanks cannot be repaired. RV holding tanks are expensive to replace.

Repair an RV Black Tank

Move the RV to an outdoor area. Locate the damaged area on the tank. If the tank is empty, fill it with clean water before proceeding.

Put on safety glasses and disposable gloves. Use a cordless drill to drill a hole in each end of the crack to prevent it from becoming larger. If there is a hole larger in diameter than a quarter or if the crack is longer than a dollar bill, the tank cannot be repaired and must be replaced. Use sawdust to absorb any puddles that form.

Empty the tank by taking it to an appropriate dumping station. Wear gloves and use the proper tank hose assembly. Do not empty blackwater into a driveway or storm drain as it poses a hazard to human health.

With the rig parked outdoors, rough up the damaged area with coarse grade sandpaper. Brush or wipe away as much dirt and dust as possible. Wipe the area with a rag soaked in acetone. Dry with a clean rag.

Measure the damaged area and use scissors to cut a piece of fiberglass cloth that is larger than the damaged area by 1 inch in every direction.

Put on clean gloves and wear safety goggles. Remove the resin bag containing the tube from the Seal-N-Place kit. Keeping the bag sealed, break the tip off of the tube. Turn the key at the end of the tube to completely squeeze the tube's contents into the resin bag.

Combine the contents of the bag by squeezing and kneading it for a few seconds. Work quickly from this point on, the resin will harden completely in six minutes.

Open the bag. Generously apply the resin mixture to the damaged area and beyond using a craft brush. The resin should extend past the damaged area about an inch in all directions.

Cover the resin area with the fiberglass cloth, smoothing it down with a gloved hand to remove all bubbles, bumps and creases. Paint the entire piece of fiberglass cloth with the resin mixture; hold the cloth in place with one hand and paint it with the other. Taper the edges of the cloth by smoothing down to create professional looking finish. Allow the repair to dry completely.

Items you will need

  • Safety glasses
  • Cordless drill and drill bit
  • Absorbent material such as sawdust
  • Tank hose kit
  • Coarse grade sandpaper
  • Disposable gloves
  • Acetone
  • Shop rags
  • Scissors
  • Fiberglass cloth
  • Disposable craft or paint brushes
  • Syon Seal-N-Place


  • Only use acetone in a well-ventilated area. The fumes are hazardous.


  • "Trailer Life's RV Repair & Maintenance Manual"; 4th Edition, by Bob Livingston; 2002.

About the Author

Lynda Altman started writing professionally in 2001, specializing in genealogy, home-schooling, gardening, animals and crafts. Her work has appeared in "Family Chronicle Magazine" and "Chihuahua Magazine." Altman holds a B.A. in marketing from Mercy College, a black belt in taekwondo, master gardener certification, a certificate in graphic arts and a certificate in genealogy.

Photo Credits