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This guide covers the Seaflo 21 Series 12 V pump installed in your trailer. Your pump is controlled by a Pump switch on the control panel. The fresh water tank is under the bed, and the pump is mounted under the sink in the galley. Water flows from the tank → pump (under sink) → galley faucet. The faucet has its own valve. The pump has a built-in pressure switch, so it can stay ON while you’re camped; it wakes up automatically when you open the faucet and goes back to sleep when you close it.

Important: Always turn the pump OFF for transit (towing) and whenever you’re away from the trailer.

Normal Operation

  1. Water onboard — Make sure your fresh tank has water.

  2. Pump ON — Flip the Pump switch on the control panel.

  3. Use water — Open the faucet valve in the galley. The pump will run only while pressure drops, then stop by itself.

  4. Camp best practice — It’s fine to leave the Pump switch ON while camped. Turn it OFF at night if you suspect any leaks.

  5. Before driving / storing — Close the faucet and switch the Pump OFF.

Tip: After the trailer sits or after you’ve drained lines, you may get sputter/air for 10–30 seconds. That’s normal—let it clear.

Safety & Care

  • Never run dry on purpose. If there’s no water flow after ~30 seconds, turn the pump OFF and troubleshoot.

  • Electrical: The pump is on a fused 12 V circuit. If a fuse is blown, replace only with the same rating printed on the fuse row.

  • Leaks: Paper towel under each fitting is a great “leak detector.” Any drip = fix before use.

  • Winter: If you see slush or suspect freezing, don’t run the pump until everything is thawed and checked.

Quick Things to Check

  • Tank level: There must be water in the fresh tank (under the bed).

  • Pump switch: Is the Pump switch actually ON?

  • Faucet valve: Is the galley faucet opened when you expect flow?

  • Hose path: Follow the suction hose from the tank (under bed) to the pump (under sink), then the outlet hose to the faucet—no kinks, no loose connections?

  • Strainer (under sink): Most Seaflo pumps have a clear bowl strainer on the inlet right next to the pump under the sink. If it’s full of debris/air, clean and reseat it.

  • Battery: Very low battery = weak or no pump. If lights are dim or your monitor shows low voltage, recharge first.

Troubleshooting by Symptom

1) Pump doesn’t run at all (no sound)

  • Pump switch OFF or bad contact → Flip Pump ON; toggle it once.

  • Blown DC fuse → Check the DC fuse panel for the “Water Pump” fuse. Replace with the same amp rating.

  • Low / dead battery → Recharge or connect shore power and try again.

  • Loose wiring at pump → Open the under-sink cabinet and check the two pump power leads.

  • Still dead? Turn pump OFF and contact support—could be a failed switch or pump.

2) Pump runs but no water comes out

  • Empty tank / closed tank valve → Fill tank; ensure any inline tank valve is OPEN.

  • Air-locked / lost prime → Open the galley faucet fully (cold side), run pump up to ~30 sec. If no flow, stop, crack the under-sink strainer bowl to release air, retighten hand-snug, try again.

  • Clogged inlet strainer (under sink) → Unscrew the clear bowl, rinse the screen, wet the O-ring, hand-tighten—don’t over-tighten.

  • Kinked or reversed lines → Verify the arrow on the pump body points from tank → faucet; fix any sharp bends.

3) Water spits/foams or pressure is weak

  • Air in lines → Open the faucet fully and let it run until the stream is steady.

  • Low tank level → Refill tank (pickup can suck air when low).

  • Clogged aerator (inlet of faucet) → Unscrew, rinse, reinstall.

  • Partially clogged strainer (under sink) → Clean as above.

  • Battery on the low side → Recharge; diaphragm pumps slow down with voltage sag.

4) Pump short-cycles with all faucets closed (clicks on/off every few seconds)

  • Very small leak on the pressure side → Check every fitting from under-sink pump outlet to faucet. Look for damp towels or drips.

  • Faucet not fully closed → Turn handle fully off.

  • Air leak on the inlet (suction) side → Reseat strainer bowl and inlet fittings under the sink; a tiny suction leak will cause cycling.

  • Normal vs not → A brief run every few minutes can be normal; every few seconds is not—chase leaks.

5) Pump won’t stop running

  • Open valve or real leak → Confirm the faucet is closed; look for drips in the under-sink area and in the galley.

  • Suction-side air leak (under sink) → The pump can’t build pressure if it’s sucking a little air. Reseat/retighten the inlet fittings and strainer.

  • Clogged outlet / frozen line → If it’s cold, thaw lines. Check the faucet aerator isn’t blocked.

  • If it still won’t stop after checks, turn pump OFF and call support—pressure switch or internal check valve may need service.

6) Pump is noisy or vibrates a lot

  • Mounting feet hard against wood/metal → Under the sink, make sure the soft rubber feet are intact and screws are snug (not cranked).

  • Pipes touching walls → Add a little slack or a cushion where hoses touch cabinetry.

  • Cavitation (growling sound) → Usually suction-side air/strainer issue; clean/reseal the under-sink strainer and confirm a smooth inlet hose path.

  • Low voltage → Charge battery; under-voltage makes motors growl.

How to Prime (after draining, filter service, or long storage)

  1. Fill the fresh tank (under bed).

  2. Open the galley faucet to the cold side.

  3. Turn Pump ON and wait up to 30 seconds.

  4. Once you get steady flow (no spurts), close the faucet.

  5. Inspect the under-sink strainer and fittings for leaks. Repeat for the hot side if your trailer has one.

If the pump won’t prime: turn pump OFF, remove and fill the under-sink strainer bowl with clean water, reinstall, and try again.

Cleaning the Inlet Strainer (under the sink)

  1. Turn Pump OFF.

  2. Place a towel under the strainer.

  3. Unscrew the clear bowl (hand-tight only).

  4. Rinse the screen and bowl.

  5. Wet the O-ring so it seats nicely; reinstall bowl hand-snug.

  6. Turn Pump ON and check for leaks.

Sanitizing the System (taste/odor issues)

  • Mix ¼ cup unscented household bleach per 10 gal of water in the tank.

  • Run the faucet until you smell bleach, then let sit 4–6 hours.

  • Drain and flush with fresh water until the smell is gone.

Winter & Freezing Weather

  • If you suspect a freeze, do not run the pump until thawed and inspected—ice can crack fittings and the pump head.

  • For winterizing (RV antifreeze), use only non-toxic RV/Marine antifreeze and follow your trailer’s winterize/bypass procedure. Flush thoroughly before drinking.

Spares & Handy Tools

  • Correct-rating spare fuse for the pump circuit

  • Towels/paper towels (leak checks)

  • Phillips screwdriver; adjustable wrench

  • Food-grade silicone grease (for strainer O-ring)

When to Contact Us

  • Pump blows the fuse repeatedly

  • You smell hot electrical/plastic

  • Continuous leaks you can’t locate

  • Pump won’t prime after the under-sink strainer procedure

  • Continuous running or rapid cycling after you’ve ruled out leaks and air

Quick Recap

  • Pump ON while camped, OFF for transit.

  • Open faucet valve to use water; the pump runs only when needed.

  • Most issues are air/strainer (under sink), empty tank (under bed), or a small leak—check those first.

User Manuals:

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