Dishwasher Not Draining

A dishwasher that won't drain usually leaves standing water pooled at the bottom of the tub after a cycle finishes. The most common cause is a clogged drain filter, though a kinked drain hose, a faulty drain pump, or an unremoved disposal knockout plug on a new installation can also be responsible, and each has a fairly distinct pattern to it. 

Common Causes 

• Clogged drain filter. Food debris collects in the filter at the bottom of the tub, and once it's packed too tightly, water can't pass through fast enough to drain properly between cycles, leaving a pool behind even though the cycle otherwise runs normally through wash and rinse. 
• Kinked drain hose. The hose that carries water out to the sink drain or garbage disposal can kink if the dishwasher has been pushed back too far or the hose wasn't routed properly during installation, restricting or blocking water from draining out completely, sometimes only partially at first. 
• Faulty drain pump. The pump pushes water out of the tub and through the drain hose. If the motor weakens or the impeller gets jammed with debris, water has nowhere to go even if the filter and hose are completely clear and free of blockages, since the pump itself is the last stage in the process. 
• Disposal knockout plug not removed (new installs). If your dishwasher drains into a garbage disposal, the disposal has a knockout plug that must be removed before the first connection. If it's left in place, water backs up every single cycle no matter what else is working correctly on the dishwasher side. 

When to DIY vs. Call a Pro 

You can safely remove and clean the drain filter, check behind the dishwasher for a kinked hose, and if you have a garbage disposal, confirm the knockout plug was removed, which is a common oversight after a new dishwasher or disposal install. It's also worth checking whether the issue started right after a kitchen renovation or new appliance installation, since that timing is a strong clue toward the knockout plug. Diagnosing a faulty drain pump means accessing the machine's internal components, which is a job for a technician. 

FAQ 

How do I check if the disposal knockout plug is still in? 

Look inside the disposal's dishwasher inlet, usually on the side facing the dishwasher, for a small plastic or metal disc. If your dishwasher has never drained properly since a new disposal was installed, this is one of the first things worth checking before assuming a bigger part has failed or booking a repair visit. 

Is a small amount of water in the bottom of the tub normal? 

A little water sitting around the drain area between cycles is normal on some models and helps keep the drain seal from drying out. Standing water covering the bottom of the tub, or deep enough to see clearly, points to an actual drainage problem worth investigating rather than something to ignore. 

Can food waste in the drain hose cause a blockage on its own? 

Yes, especially if dishes aren't scraped before loading, food particles can build up inside the hose over time even if the filter is regularly cleaned, since the hose sits further down the drainage path where it's harder to inspect without disconnecting it. 

Will running the disposal help clear a dishwasher drainage issue? 

If your dishwasher shares a drain line with your garbage disposal, running the disposal briefly can help clear debris that's blocking shared plumbing, which is worth trying before assuming the dishwasher itself has failed or needs a technician. This is one of the quickest checks to rule out on this list. 

Is this an expensive repair? 

A clogged filter or kinked hose costs nothing to fix yourself, and even a drain pump replacement is generally a moderate repair rather than an expensive one compared to replacing the dishwasher entirely, which usually costs several times more once installation is included. 

If the filter, hose, and knockout plug all check out fine, Boreal can diagnose and repair the drain pump properly, backed by a 90-day warranty on parts and labour for every job.