Dishwasher No-Drain Repair Standard

Purpose

Standing water in the bottom of a dishwasher is the most over-parted fault in residential appliance repair. The drain pump is the obvious suspect, it is on the van, and it is the wrong part on a large share of these calls. This standard forces the drain path to be proven open on its own before any pump is condemned.

The failure it prevents: a disposal installed by somebody else with the dishwasher inlet knockout plug still in place, and a tech who fits a healthy pump and hands back a machine that still holds water. The part is not returnable once fitted and the second visit is free.

Scope

Residential and light commercial undercounter dishwashers that fill and wash but leave water in the tub at cycle end, or report a drain fault code. It covers the sump, filter assembly, check valve, drain pump, drain hose, the air gap or high loop, and the disposal or waste tee the hose lands on.

It does not cover a dishwasher leaking onto the floor: that is the dishwasher leak repair and seal replacement standard, with the damage side owned by the dishwasher leak response SOP. It does not cover replacing the disposal, nor drain piping past the trap arm.

Roles and the handoff between them

Before the toe kick comes off

Water is standing in a cabinet that also holds the receptacle. The appliance circuit goes off at the panel and is locked and tagged before any hand goes behind the toe kick. A wall switch is not an isolation.

Prove dead, do not assume dead. Meter proved on a known live source before and after the reading, per NFPA 70E-2021, 120.5, with work practices per 29 CFR 1910.333(b)(2). Those practices are written for qualified persons under 29 CFR 1910.332 and 1910.399, so if nobody on site is qualified for the panel work, the isolation goes to an electrician and the visit stops.

Tub water can scald. A machine stopped in or after a heated wash holds water hot enough to burn over a hotter element. Keep hands and the vacuum hose out until the water is comfortable against a gloved hand.

Sump water is food waste held warm, so it is a biological contact route. Nitrile gloves for any hand in the sump, hands washed before eating or leaving, and what splashes goes on your towel.

Nothing enters a disposal grind chamber by hand while its circuit is live. Its wall switch is not an isolation: off at the panel, locked, tagged and proved first.

The procedure

1. Confirm the fault on the machine as found, powered. Read the water level against the filter assembly and pull any stored code. Acceptance: water at or above the top of the filter assembly, or a stored drain code. Wrong looks like a thin film below the filter, which is normal residual. Stop rule: a dry tub with a wet floor is a leak call, so close this SOP. Hazard: the door is open on a possibly hot tub on a live machine, so read the level by eye and keep hands out of the sump.

2. Isolate the appliance circuit, lock and tag it, prove dead at the appliance terminals. Acceptance: 0 V line to neutral and line to ground, meter proved live on a known source before and after. Wrong looks like a meter reading zero everywhere including the known live source, which is a blown meter fuse giving a believable zero. Stop rule: any voltage present, or a meter that will not prove live, means stop and re-identify the circuit. Hazard: panel work, so stand to the hinge side of the door and take the jewellery off.

3. Bail the tub, then strip the sump to the pump inlet. Remove standing water, then lift out the filter assembly, coarse screen and spray arm. Acceptance: sump empty and dry to the touch, pump inlet visible with nothing across it. Wrong looks like a filter matted with grease and label paper, or glass on the screen. Stop rule: glass or metal fragments are picked out with pliers and logged, never flushed onward. Hazard: glass and food-waste bacteria share this step, so cut-resistant gloves under nitrile and no blind reaching under the spray arm.

4. Work the check valve and turn the impeller by hand. Move the flap or ball valve in the sump outlet through its travel, then rotate the impeller with a small hook. Acceptance: the valve returns closed under its own weight or spring, and the impeller turns a full revolution with light drag and no grinding. Wrong looks like a valve gummed open, which back-siphons sink water into the tub, or an impeller locked by a fruit pit. Stop rule: an impeller that frees and turns cleanly is retested at step 6; one that will not free is a pump replacement. Hazard: the impeller edge is sharp and the cavity hides glass, so use a tool.

5. Prove the drain path downstream, off the machine, before any part is condemned. Pull the hose off the disposal nipple or waste tee into a pan, then pour roughly 1 quart of water into that nipple. Acceptance: the quart disappears within a few seconds, and the same quart runs cleanly through the hose you removed. Wrong looks like water standing in the nipple, which is the knockout plug still in place. Stop rule: a blocked nipple is knocked through from the inlet side and the slug lifted out by hand with that circuit off, locked, tagged and proved at step 2 conditions, then the pour repeated; a blocked line past the tee is a plumber's call. Hazard: a hand goes inside a grind chamber here, which is why its circuit is locked out.

6. Reconnect, restore power under control, and command a drain. Refit the hose with a new clamp, remove the lock and tag, close the breaker, run the drain function with the door closed. Acceptance: the pump runs within a few seconds and the sump empties below the filter seat. Wrong looks like a pump that hums without moving water, or one silent with supply voltage present at its terminals during the drain phase, which is the condemning finding. Stop rule: no operation with voltage at its terminals means fit a pump; no voltage there during a drain command means the fault is upstream in the control. Hazard: energy goes back in with the cabinet open, so stand clear of the panel door as the breaker closes, then open the door mid-drain to confirm the pump stops, proving the door interlock still works.

7. Reinstate the high loop or the air gap and secure the hose. Route the hose up to the underside of the countertop and strap it, or refit the listed air gap fitting on the sink deck. Acceptance: the top of the loop sits above the flood rim of the sink with the cabinet doors shut, or the air gap cap is seated and both hoses clamped. Wrong looks like a hose lying flat on the cabinet floor, which siphons sink water back into the tub and produces a repeat no-drain call on a healthy pump. Stop rule: nothing to strap to and no air gap fitted means quote the fitting rather than leaving the hose loose. Hazard: fasteners go overhead into counter substrate, so eye protection on.

8. Run one full normal cycle, then close out and restore the enclosure. Racks back in, watch the fill, wash and drain, then check under the machine and inside the cabinet. Acceptance: tub empty below the filter seat at cycle end, cabinet floor dry, no drips at the clamp, no stored code. Wrong looks like a slow final drain leaving water at the filter seat, which means the path is only partly restored. Stop rule: any water above the filter seat sends you back to step 5, not to the parts catalog. Hazard: the machine has been running hot, so let the area dry before the toe kick and mounting bracket go back, both refitted before handover.

The record this produces

A drain record on the ticket and on the equipment file, readable by the next tech.

• Machine: model, serial, age, and the stored codes read at step 1 and again at step 8.
• Found: water level against the filter seat, and what came out of the sump and filter.
• Downstream test: the 1 quart pour result at the nipple or tee, stated as ran or blocked, and what the blockage was.
• Pump verdict: voltage present or absent at the pump terminals during the drain command, and whether the pump ran. Those two facts are the whole condemnation, and they are the fields a warranty claim asks for.
• Discharge arrangement: high loop with strap, or listed air gap, and which was there on arrival.
• Parts and handover: anything fitted with its date, and what the customer was told.

The knockout line matters most. It is the field that stops a shop replacing the same pump twice.

One run of this standard, filled in

A six-year-old undercounter dishwasher, water in the bottom after every cycle. The ticket notes the customer changed the disposal himself two weekends ago.

• Step 1: water level at the top of the filter assembly, one stored drain code. Pass.
• Step 2: breaker locked and tagged. Meter proved live, read 0 V at the terminals, proved live again. Pass.
• Step 3: about 2 quarts bailed. Filter matted with grease, no glass. Sump dry, inlet clear. Pass.
• Step 4: check valve returns closed. Impeller turns a full revolution, light drag, no grinding. Pass.
• Step 5: hose off the disposal nipple, 1 quart poured in. Water stands in the nipple and does not fall. Fail. Stop rule taken: knockout plug still in place from the disposal install. Disposal breaker opened, locked, tagged and proved dead, plug knocked through from the inlet side, slug lifted out by hand, pour repeated and the quart ran straight through. The hose passed the same quart cleanly.
• Step 6: hose refitted with a new clamp, lock and tag off, breaker closed. Pump ran in about two seconds, sump emptied below the filter seat, discharge seen at the sink. Door opened mid-drain and the pump stopped, so the interlock is intact. Pass, and no pump is fitted.
• Step 7: hose was lying flat on the cabinet floor. Strapped to the underside of the counter above the sink flood rim. Pass.
• Step 8: full cycle run. Tub empty below the filter seat, cabinet floor dry, no drips, no stored code. Toe kick refitted. Pass.

The job turned on step 5, which costs about the time it takes to boil a kettle. Run in the other order, this tech reads a matted filter at step 3, decides the pump is tired, and leaves a machine that still holds water with a non-returnable part in it.

When the call does not run as written

The sink itself will not drain. Stop before the machine is opened further. The dishwasher discharges into a line that is already full, so nothing done to the appliance helps. Hand to a plumber and book the retest for after the line clears.

The knockout was driven in and the slug never came out. It will jam the flywheel or come back up the branch. Retrieve it with the circuit locked and tagged, and if it cannot be found, write that down rather than running the disposal to find out.

The machine drains on a direct drain command but not on a full cycle. That points at the control commanding the drain phase, not at the path. Do not fit a pump; cross-refer to the control board replacement and configuration SOP.

No air gap and nothing to strap a high loop to. Say plainly the arrangement does not meet the requirement, quote the fitting, note the refusal if declined. Whether a high loop is acceptable at all depends on which plumbing code, in which edition, your jurisdiction has adopted.

References

• The manufacturer's service data and tech sheet, which carries the sump exploded view, the drain pump terminal identification and the fault code table. The pump condemnation depends on which terminal you read.
• NFPA 70E-2021, 120.5 for the proved live, dead, live sequence, with work practices at 29 CFR 1910.333(b)(2) and the qualified person definitions at 29 CFR 1910.332 and 1910.399.
• The plumbing code your jurisdiction has adopted, in the edition it has adopted, for whether the discharge requires a listed air gap fitting or permits a high loop.
• See related: the dishwasher leak repair and seal replacement standard, the garbage disposal replacement standard, and the control board replacement and configuration SOP.