Question

I have a Liberty 404 that pumps from a basement sink.

The washer now drains into that sink, and it smells.

Can I tie the washer discharge straight to the 404?

I planned a trap between the washer and the pump.

I also thought about a check valve on the washer line.

Answer

Yes, connect the washer to the Liberty 404, but not with a trap or a check valve on the washer line. Use a vented 2-inch standpipe with its own P-trap. Drain that trap by gravity into the 404 inlet. Put the check valve on the 404 discharge riser only. Vent the 404 tank to the building vent. Seal the basin lid and grommets tightly.

Why your first plan smells

A trap to a sealed basin will often self-siphon.

That leaves a dry trap and lets odor escape.

A check valve in a gravity line is a lint magnet.

It adds clogs without fixing venting issues.

Clean, code-friendly layout

• Install a 2″ standpipe, 18–30″ tall above its P-trap.
• Vent the trap per your local code requirements.
• Run the trap arm by gravity to a 404 inlet grommet.
• Hard-vent the 404 tank to the house vent system.
• Place a check valve and union on the 404 discharge.
• Keep about 1/4″ per foot slope on gravity runs.
• Use a lint filter on the washer hose if needed.

Step-by-step

1. Set the standpipe and 2″ P-trap beside the washer.
2. Vent the trap and tie into a legal vent point.
3. Drill the 404 inlet and fit the supplied grommet.
4. Slope the trap arm into the basin inlet by gravity.
5. Pipe the 404 discharge up with a check valve and union.
6. Tie the discharge into the building drain above grade.
7. Run water and test the float, discharge, and seals.

Rich Media Diagram

Download the 900×900 diagram (PNG)

Helpful resources

• Liberty Pumps 404 product page
• International Code Council (venting and traps)
• Standpipe height basics