Laundry room: the plumber cut the washer standpipe off at 12 inches above the trap to fit under the counter, used a 1-1/2 inch P-trap, and pushed the washer hose into the pipe with a rubber grommet so 'it wouldn't splash.' Washer supply valves are plain quarter-turn ball valves with no arrestors.

Multiple code violations and flood risks. Do not use until corrected.

1. Standpipe Height (IPC 802.4 / UPC 804.1): Standpipe must be 18" minimum to 30" maximum above the trap weir. At 12", the trap seal will siphon dry during discharge, allowing sewer gas entry and potential backflow.
2. Trap Size (IPC 802.3 / UPC 702.1): Clothes washers require a 2-inch trap and standpipe. A 1-1/2" trap restricts the high-volume discharge rate (up to 15+ GPM), guaranteeing overflow.
3. Hose Connection (IPC 802.4.3 / UPC 804.1): The drain hose must not be sealed into the standpipe (grommet/caulk/tape). An air gap is required to prevent siphoning wash water back into the machine (cross-connection) and to relieve pressure. The hose terminates in the standpipe, secured only by a hook/strap.
4. Water Hammer Arrestors (IPC 604.9 / UPC 609.10): Required on both hot and cold supply lines at the washer box. Quarter-turn ball valves close instantly; without arrestors, hammer damages pipes, valves, and the washer’s internal solenoids.

Required Fixes:

• Re-pipe standpipe to 2" PVC/ABS, 18"–30" above trap weir.
• Install 2" P-trap.
• Remove grommet; secure hose with air gap per manufacturer specs.
• Install certified water hammer arrestors (AA size min) at supply box.
• Ensure standpipe is vented within trap arm limits (typically 5–6 ft for 2").

This requires a licensed plumber. Current setup risks sewage backup, machine damage, and structural water damage.

Yes, there are multiple code and safety issues here:

1. Standpipe height: The standpipe must be 18 to 42 inches above the trap weir (IPC 704.3, UPC 704.3). Cutting it to 12" is too low and risks siphoning the trap or backflow during drain cycles. Minimum 18" is required to maintain the trap seal.

1. P-trap size: A 1-1/2" P-trap is acceptable for a clothes washer (IPC 704.2), but the standpipe must be at least 2" diameter (IPC 704.3). If the standpipe is only 1-1/2", it’s undersized and prone to clogging and slow drainage.

1. Hose connection: Pushing the washer drain hose into the standpipe with a rubber grommet is not code-compliant. The hose must be secured with a clamp or fastener to prevent dislodgement during the spin cycle (IPC 704.3 Exception). A loose hose can flood the laundry room.

1. Supply valves: Quarter-turn ball valves are fine, but lack of water hammer arrestors is a concern if the valves close quickly (common with solenoid valves in washers). While not always required by code for residential washers, IPC 604.9 recommends arrestors where quick-closing valves cause water hammer. Install arrestors on both hot and cold lines to protect pipes and valves.

Fix:

• Replace standpipe with a minimum 2" diameter pipe, extending 18 to 42" above the trap weir.
• Use a proper 2" standpipe with a P-trap (1-1/2" or 2") and secure the drain hose with a clamp.
• Add water hammer arrestors on both supply lines.
• If the counter blocks height, consider a low-profile washer or relocating the plumbing—do not sacrifice code compliance for fit.

If unsure, consult a licensed plumber. Improper drainage risks flooding, sewer gas entry, and fixture damage.