How To Unclog an RV Toilet

Years ago, a friend invited me to spend the night as a guest in his custom Prevost RV. It was stunning and luxurious, until I accidentally overflowed the toilet.

That was my last invite over there. But because of that incident, I learned a valuable lesson on how to properly use and unclog an RV toilet. Put on your personal protective equipment (PPE) and let’s take a look.

How Do RV Toilets Work?

Modern RV toilets are similar to household toilets, with some of the higher-end ones even made from porcelain. But there are two primary differences:

• Most RV toilets empty directly into a holding tank, so waste does not go through a trap.
• Most RV toilets use a foot pedal instead of a hand lever for flushing. Partially depressing the foot pedal adds water to the bowl, while fully depressing it opens the seal to the blackwater tank, flushing the toilet.

RV systems also require special toilet papers that rapidly break down so they don’t clog the blackwater tank or damage the in-tank sensors.

How To Unclog an RV Toilet

Out of all of the tasks in maintaining your RV, this is surely the least pleasant. Your first step will be identifying what type of clog you’re dealing with. It will be either an obstruction blocking the door seal into the blackwater tank, or a clog below the seal.

In most RVs, the sealed door opens directly into the tank, offering a full view. That makes this easy to determine the type of clog.

If it’s just a clog blocking the door seal, and if your toilet empties directly into the blackwater tank, simply use a sturdy stick to push the waste obstruction down into the tank. If it’s something other than waste, like a towel, you’ll need to remove it upward instead so it doesn’t create another clog farther down the system.

However, the most common blockages occur below the seal, usually what’s called a pyramid plug clog. They’re apt to form when you’re using your toilet in an RV park for several days with the drain valve open. As time goes by, all the liquids run out, leaving a dense conical shape of waste pointing up toward the door seal.

(To whoever coined the term for this, all I can say is, ick, you scored a 10 on the gross imagery scale!)

If you have the less-common RV plumbing setup that includes an elbow of pipe between your toilet and the blackwater tank, a clog can also happen there. Regardless of your system’s configuration, here’s how to resolve a below-seal blockage.

Tools and materials

• A three- to eight-foot length of 3/4-in. Pex pipe, with length depending on whether you have a direct mount or piping;
• Two or more bottles of RV black tank clearing fluid;
• Flexible water wand designed for spraying out RV tanks;
• Eye protection, gloves and any other PPE you deem necessary for your level of comfort.

Steps To Unclog an RV Toilet

1. Determine if you have a direct-flush or a piped-flush system (see above).
2. Turn off the freshwater supply to the toilet so you can open the valve with no water. Make sure the blackwater tank valve on the outside is also closed.
3. Slowly pour one bottle of RV tank clearing liquid into the toilet. This helps break up the blockage.
4. Observe how fast the product goes down the toilet. If there’s no movement, let it sit for 24 to 48 hours. If it’s moving, proceed immediately to the next step.
5. Insert the flexible Pex pipe into the toilet opening. Move it around, up and down and at angles to break up the blockage.
6. Pour water slowly into the toilet. If the water drains faster than it did before pouring in the tank clearing fluid, turn the water back on and flush the toilet.
7. If it flushes but remains slow, add a second bottle of tank clearing liquid and flush three to six more times. If it’s still clogged, let it sit for 24 to 48 hours to give the fluid more time to dissolve the blockage. If it’s only mostly cleared, continue to use toilet normally for the next 24 hours, then empty the blackwater tank as you normally would.
8. After emptying the tank, use a flexible RV tank spray water wand to shoot water into the blackwater tank from outside, thoroughly rising it out to free any other materials that may be attached to the inside of the tank. Add another bottle of tank clearing fluid if needed.

How To Prevent Future Clogs

• Never leave the blackwater tank’s exterior valve open while hooked up to an RV park sewer system. Leaving it open allows the liquid waste to immediately drain from the tank, which creates a pyramid plug clog.
• Do not use regular toilet paper. RV toilet paper is specifically designed to biodegrade rapidly, preventing blockage and damage to in-tank sensors.
• Keep plenty of water in the blackwater tank. When in doubt, flush an extra time or two when you take a number two.
• Regularly add odor and waste-controlling chemicals to expedite the breakdown of solid waste.
• Never store your RV with waste in the blackwater tank. Instead, keep a little water in there and the odor and waste-control additives.