How to Clean and Maintain a HepvO Waterless Valve in Your RV

The best thing about a HepvO waterless trap is how little it asks of you. Wavin, the company behind HepvO, says in its RV installation instructions that no routine or seasonal maintenance is required. There's no water seal to top up, nothing to winterize at the fixture, and no trap primer. Still, a drain is a drain. Grease, soap scum, hair and food bits all pass through the valve, and sooner or later you'll want to flush it, clear a clog downstream or blow out the lines for winter. Here's how to do each one without damaging the membrane, based on Wavin's own guidance.

What's inside the valve

A HepvO is a polypropylene tube with a flexible membrane inside. Water draining from the sink pushes the membrane open. When the flow stops, it closes again and seals against tank air. That membrane does the job a P-trap's water seal used to do, so every rule below is about keeping it clean, flexible and undamaged.

Routine care: hot water and nothing else

For day-to-day use, the simplest habit is the best one: finish washing up by running hot tap water down the drain for half a minute. That carries grease and soap film through the valve before it can cool and stick to the membrane. On kitchen sinks, scrape plates into the trash and keep cooking fat out of the drain, which is good practice for your gray tank anyway.

Using drain cleaners with a HepvO

You don't have to pull the valve out to use an ordinary drain cleaner, but check the label first. Wavin's guidance says:

• Caustic drain cleaners are fine. HepvO is resistant to standard caustic-based (lye-type) drain cleaners.
• Mild acid cleaners are fine up to 10%. The RV instructions rate the valve for acid-based cleaners with concentrations up to 10%.
• Remove the valve for anything stronger. If you're flushing with a higher-concentration acid cleaner (for example, a strong sulfuric-acid drain opener), take the HepvO out first.
• Flush it straight through. Wavin's manual says all cleaning agents should be flushed through right after use. Don't let a cleaner sit in the valve overnight.

Whatever you use, finish by rinsing with plenty of clean water. Wavin calls a clean-water rinse good practice after any maintenance.

Clearing a clog: take the HepvO out first

This is the one rule that really matters. Never push a drain snake, auger or water jetter through a HepvO. Wavin says to remove the valve before using any mechanical drain-cleaning tool, because rodding through it can damage the internal parts. The good news is that a HepvO is easy to take out, and once it's off, the open pipe gives you a handy access point to clean the line downstream.

Step 1: Get ready

Put a bucket or pan and a rag under the valve. There's no trap water to catch, but whatever is sitting in the drain line above a clog will come out.

Step 2: Undo the slip nuts

Unscrew the slip nut at each end of the valve by hand and lift the HepvO out. Keep the washers and rubber seals together so they go back in the same order.

Step 3: Clean the line, not the valve

Run your snake or jetter through the open drain pipe toward the tank, with the HepvO safely out of the way.

Step 4: Rinse the valve

While it's out, rinse the HepvO under a tap from the inlet end in the direction of the flow arrow, so the water pushes through the membrane the way drain water does. Check both ends for hair, food or grease caught around the membrane. Flush it out with water rather than poking at the membrane with a tool. Wavin's instructions don't cover taking the valve body apart, so leave it assembled.

Step 5: Reinstall it the right way round

• Flow arrow toward the tank. The direction of flow is marked on the body, and the valve only works one way.
• Ribs down if it isn't vertical. If the valve runs horizontally or at an angle, Wavin says the ribs must be on the bottom so the valve drains properly, with at least 1/8" of fall per foot.
• Hand-tight, no sealant. Seat each washer square and tighten the slip nuts by hand. Wavin says not to use jointing compound or chemical sealant on HepvO connections.

Then run hot water hard and check each joint with a dry paper towel. Our HepvO install guide covers seating the washers and leak-testing in more detail.

Winterizing: keep compressed air under 100 psi

A HepvO holds no water, so there's no trap to fill with antifreeze at that fixture. If you blow out your drain lines with compressed air, Wavin's RV instructions say not to exceed 80–100 psi. Set your regulator before you connect the blow-out plug. For the rest of the job, see our step-by-step RV winterizing checklist.

Signs your HepvO needs attention

• Slow draining at one fixture only. Something is probably caught in the membrane or the line just below it. Try a hot-water flush, then remove and rinse the valve.
• Odor returning at a sink that has a HepvO. Debris can hold the membrane slightly open. Rinse it, and check that it was installed with the flow arrow toward the tank and ribs down. If the smell continues, the problem may be elsewhere. Work through why an RV sink smells like sewer, starting with the tank vent.
• A drip at a joint. That's almost always a washer seated crooked or a slip nut that's cross-threaded. Back the nut off, re-seat the washer and hand-tighten again.
• Still leaking or not sealing after a rinse. If a clean valve, installed correctly, still lets odor through or drips from the body, replace it. A new HepvO kit costs less than chasing the problem. If your sink has a 1-1/4" tailpiece, get the BV1B/UA kit instead.

FAQ

How often should I clean a HepvO valve? Wavin says no routine or seasonal maintenance is required. Clean it when a drain slows down or after you've cleared a clog, and rinse it with clean water whenever you've had it out.

Can I pour boiling water down a HepvO? Hot tap water is the safe choice. Wavin's instructions don't give a boiling-water rating for the valve, so we don't recommend it.

Can I use Drano or a similar drain cleaner? Standard caustic drain cleaners are fine according to Wavin. Flush them through with water straight away. For acid cleaners above 10%, remove the valve first.

Can I snake the drain with the HepvO in place? No. Remove the valve first. Pushing a snake or jetter through it can damage the internal parts.

Do I need antifreeze in a HepvO? No. It holds no water, so there's nothing at the fixture to freeze. Just keep any blow-out air at or below 80–100 psi.

Still deciding whether to switch from a P-trap? Read our HepvO vs generic waterless traps vs a traditional P-trap comparison.