The short answer
Standing water in a BlueStar tub is usually the filter and the sump beneath it. If the machine is newly installed or a disposer was recently replaced, check the knockout plug next, because the machine cannot drain until it is out. The pump itself is last.
What you observe
- Water standing over the filter at the end of a cycle — Not a film but a pool, deep enough to see.
- The machine hums during the drain and nothing leaves — The pump is powered and working against a blockage.
- It drains slowly and the dishes come out wet and dirty — A partial restriction affects both wash pressure and drainage.
- Water appears in the sink when the machine drains — The shared drain or disposer is backing up, not the machine.
- NEAR MISS - a small amount of water left in the sump — A cupful in the sump is normal and keeps the seals wet.
Causes, most likely first on this brand
- A loaded filter and a blocked sump — First on this machine. The filter traps everything, and once it and the sump below are packed the pump cannot move water at all. Glass and labels are the usual culprits.
- A disposer knockout plug still in place — Second, on new installs and any machine whose disposer was replaced. The plug seals the dishwasher inlet from the factory and must be driven out; until it is, the hose ends at a closed pipe.
- A drain hose without a high loop, or a kinked hose — Third. The hose must rise before it falls, or the machine will not lift water out of the sump. A hose crushed behind the cabinet does the same thing.
- A blocked air gap at the sink — Fourth, where one is fitted. Debris collects in the air gap fitting and water then backs into the tub or spills onto the counter.
- A failed drain pump — Last. Silence during the drain phase rather than a hum is what points here, and it is the only cause that is not an owner check.
Check in this order, and why
- Bail out the standing water and take the filter out — You cannot assess anything else until the sump is visible.
- Listen during a drain-only cycle — A hum means powered and blocked; silence means the pump is not running.
- Ask whether anything was installed or replaced recently — A new disposer makes the knockout plug the likeliest cause by far.
- Look under the sink at the hose route and the air gap — The high loop and the air gap are both visible in a minute.
What an owner can safely check
- Bail the tub and clean the filter and sump — Sponge the water out, twist the filter out, and clear the sump of glass, labels and seeds by hand.
Tools: sponge, jug, brushAbout 30 min
- Check the disposer inlet for the knockout plug — With the disposer isolated at its switch, look into the dishwasher inlet; a plug still in place must come out.
Tools: torchAbout 15 min
- Fit or restore the drain hose high loop — Secure the hose so it rises under the counter before falling to the drain, and free any kink behind the cabinet.
Tools: screwdriverAbout 25 min
- Clean the air gap fitting at the sink — Lift the cover, remove the cap and clear the debris inside.
Tools: brushAbout 15 min
- STOP HERE if the pump is silent with a clean sump — A dead pump means the machine coming out.
Before you open anything
Safety
Switch the dishwasher off at its breaker before reaching into the sump - a built-in is usually hardwired, so there may be no plug to pull, and a capacitor can hold a charge after the power is off. Isolate a food waste disposer at its own switch before putting a hand or a tool near its inlet. Water left in the tub after a hot cycle can scald, and broken glass in a sump cuts: use a sponge and a torch rather than bare fingers.
When to call a technician
Call when the filter and sump are clean, the knockout plug is out, the hose has its high loop and the machine still will not empty - especially if the pump is silent rather than humming. Call a plumber instead if the sink backs up when the machine drains, because that is a shared drain which cannot take the flow and no dishwasher repair will change it.
Nearest pages of this class
What this page does not cover
This page covers the BlueStar built-in dishwashers generally rather than one model family, and a family-specific page is the more precise answer where one exists and is linked below. Not covered on purpose: pump part identifiers, hose diameters, air gap specifications and the height requirements for a high loop, all of which are set by the family and by local plumbing code.
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
