Mitsubishi Mini-Split Leaking Water in Burbank

Where is the water actually coming from?

A Mitsubishi wall head cools by running room air across a cold coil, which pulls humidity out as condensate. That water collects in a pan and is supposed to leave by a gravity drain line or a small condensate pump. When the line clogs with biofilm, or the pump quits, the pan fills and spills, and gravity sends it straight down the wall the head is mounted on. It looks alarming, but it is plumbing, not refrigerant. The unit usually warns you first with a P4 (drain float or sensor) or P5 (drain pump abnormal) code.

How do I tell a drain clog from something worse?

What should I do right now?

Turn the unit off at the remote or breaker to stop producing condensate, then put a towel or shallow pan under the drip to protect the floor and baseboard. In a plaster-walled Magnolia Park cottage, a day of dripping can stain and swell trim, so stopping it matters. If you are comfortable, you can try a gentle flush or a wet-vac at the outdoor end of the drain line. If the water returns or you see a P5 pump code, the pump likely needs testing or replacement, which is our call to make.

How does a tech trace the leak, step by step?

We work the condensate path from the head outward. First we pull the code: a P4 points at the drain float or sensor circuit, a P5 at the drain pump itself, a P6 says the coil is freezing (usually a dirty filter or low airflow) and the "leak" is actually melt-off. Second we check the filters and the indoor coil for ice, because a frozen coil that thaws drips like a drain clog but has a completely different cause. Third we inspect the pan and the drain connection at the head for biofilm or a slipped fitting. Fourth we test the drain: on a gravity line we confirm slope and flush it; on a pumped system we trigger the pump and watch it lift water and shut off on the float. Fifth, if the pan and pump are clean but water still appears, we check the line-set insulation, because uninsulated lines sweat and drip in a humid spell and mimic a drain leak. Each branch points at a different repair, which is why reading the code first saves a wasted part.

What is safe for me to do, and what needs a tech?

The safe homeowner moves are simple: turn the unit off to stop the drip, protect the floor and trim, rinse a dirty filter, and try a gentle flush or a wet-vac on the outdoor end of the drain line for a straightforward clog. That clears a fair share of simple cases. What crosses into pro territory is anything sealed or electrical: testing or replacing a failed condensate pump, diagnosing a cracked or slipped pan, re-pitching a drain line, and above all telling a true drain clog apart from a frozen coil caused by low refrigerant. A coil freezing on low charge is a refrigerant-circuit problem (U7, P8), not a plumbing one, and chasing it as a drain clog wastes time while the real fault gets worse. If the water comes back after a flush, or you see a P5 or P6 code, that is the line where you call us.

How do I keep it from happening again?

Annual condensate service before the summer peak is the fix. We clear and treat the drain line, confirm the pump cycles, and check the slope so the August heat wave does not catch you with a clogged line mid-run. It is one item on the broader Burbank maintenance calendar, and the same visit catches the dirty filters that cause the freeze-then-drip pattern. For the full code reference behind P4, P5 and P6, see the fault-code page.

Common questions about a leaking Mitsubishi mini-split