Everything this guide installs: Genuine HepvO 1-1/2" Waterless Sink Trap with Angled Adapter — free U.S. shipping & free 30-day returns (prepaid label, no restocking fee).
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Swapping an RV sink's P-trap for a HepvO self-sealing valve is one of the easiest upgrades in RV plumbing — slip-joint nuts thread by hand, no glue or sealant is needed on the joints, and the whole job typically takes about fifteen minutes with a bucket and a rag. Here's the full walkthrough, including the horizontal install that the angled adapter makes possible.
Before you order: two checks
- Size. Most RV kitchen sinks and showers use 1-1/2" slip-joint drains; some bathroom lavatories run 1-1/4". Look at your existing trap's nuts or measure the tailpiece outer diameter. This guide covers the 1-1/2" kit; HepvO also makes a 1-1/4" version (BV1B/UA) if that's what you find.
- Space and orientation. HepvO works vertically or horizontally. Measure the straight run below your sink tailpiece — if there isn't enough vertical drop, you'll mount it horizontally along the cabinet floor using the angled adapter included in our kit.
Tools
A bucket or pan, a rag, and at most a pair of slip-joint pliers for stubborn old nuts. New connections are designed to be hand-tightened.
Step 1 — Empty and remove the old P-trap
Put the bucket under the trap. Unscrew the slip nut at the sink tailpiece first, then the nut on the drain-line side, and let the trap's water empty into the bucket. Old traps that have never been touched may need the pliers for the first quarter turn — after that, hand pressure. Keep the old washers out of the drain line; you won't reuse them.
Step 2 — Dry-fit the HepvO valve
Slide the valve into place with the flow arrow pointing away from the sink (toward the tank). For a vertical install, the valve hangs straight off the tailpiece and connects to the drain line below. For a horizontal install, fit the angled adapter to redirect the run along the cabinet base — this is the configuration that frees up the storage space your P-trap's bend used to occupy. Check that nothing forces the plastic into a strained, side-loaded position; drain plumbing should sit relaxed before you tighten anything.
Step 3 — Seat the washers and hand-tighten
Each slip joint gets its cone washer seated square in the joint, taper facing the fitting it seals against. Thread the nuts on by hand until snug, then a final firm hand-tighten. Do not use pliers on the new joints and do not add thread sealant or PTFE tape — slip joints seal on the washer, and over-tightening is the number one cause of cracked nuts and weeps.
Step 4 — Leak test
Run hot water hard for a minute, then fill the sink a few inches and pull the plug for a full-bore drain. Wipe every joint with a dry paper towel and look for damp spots. A weep almost always means a washer seated crooked — back the nut off, re-seat, retighten. Check again after your first drive; road vibration finds lazy joints.
Step 5 — Enjoy skipping the maintenance
That's the whole job. No water seal to top up before storage, nothing to slosh out on corrugations, and at winterizing time there's no trap water to chase with antifreeze at this fixture — one less low point on the checklist in our RV winterizing guide.
FAQ
Which way does the valve face? Follow the flow arrow on the body: it points away from the sink, toward the holding tank.
Can I install it on a shower drain? Yes — same procedure, and showers benefit most because their traps dry out from disuse. Access is the only hard part on some rigs.
Do I need to vent the drain separately? The membrane resists the pressure fluctuations that check vents exist to handle, which is why many RV layouts can eliminate them. Match your rig's existing plumbing configuration.
Is any maintenance required? Essentially none in normal use — an occasional hot-water flush keeps the membrane clean. No priming, no chemicals.
Which trap should I buy in the first place? See our honest comparison: HepvO vs generic waterless traps vs a traditional P-trap.