First, Is the Water Actually a Problem?
Every heat pump produces water. In cooling mode, the indoor coil pulls moisture out of your Greater Vancouver air, and that condensate has to drain somewhere. A small puddle outside near the outdoor unit during a humid summer afternoon, or a steady drip from the outdoor unit's base in winter heating mode, is completely normal.
What is not normal is water dripping from the indoor head unit onto your floor, wall, or furniture. Mitsubishi wall-mounted units (the popular MSZ and MSY series) are designed to channel every drop into a condensate drain line. If water is escaping the cabinet indoors, something in that drainage path has failed — and it needs attention before it stains drywall or feeds mold.
If you're not sure which you're seeing, note exactly where the water appears and when. That detail helps a technician diagnose the issue faster over the phone.
The Most Common Cause: A Clogged Condensate Drain
On a ductless Mitsubishi system, condensate from the indoor head flows by gravity through a thin drain hose to the outside. Over a year or two, that hose collects dust, algae, and biofilm — a slimy buildup that loves the dark, damp interior of the line. When it clogs, water backs up into the drain pan behind the indoor unit and spills out the bottom, usually from the right or left corner.
You'll often see this start as occasional drips during the hottest, most humid days, then become a steady leak. The fix is to clear the line. A technician will flush the drain, vacuum the blockage from the outdoor end, and treat the pan to slow regrowth. On multi-head systems, the shared drain routing can make the source harder to pinpoint, which is another reason this is best left to a pro.
A related cause is a drain line that was run flat or with an upward bow during installation. Gravity drains need continuous downward slope; if yours doesn't have it, the line will pool and overflow no matter how clean it is.
Other Reasons a Mitsubishi Head Unit Leaks Indoors
Low refrigerant / frozen coil. If the system is low on refrigerant, the indoor coil can drop below freezing and ice over. When that ice melts — often after the unit cycles off — it sheds more water than the pan can handle, and it leaks. You may also notice weak cooling and the head unit running constantly. This points to a sealed-system issue that requires a licensed tech.
Dirty filters or coil. Mitsubishi units have washable filters behind the front grille. When they clog, airflow drops, the coil gets too cold, and condensation forms where it shouldn't. Cleaning the filters monthly in cooling season is the single best DIY habit.
A cracked or shifted drain pan. Older units, or units bumped during cleaning, can have a pan that no longer sits true. Water then misses the drain entirely.
A failed condensate pump. Some installs — especially basement or interior walls in Vancouver homes where gravity draining isn't possible — use a small condensate pump. If that pump fails or its float switch sticks, water overflows fast.
What You Can Safely Check, and When to Stop
It's fine to do a few things yourself. Turn the system off at the remote to stop adding water. Pop the front grille and pull the filters — if they're grey with dust, rinse them in lukewarm water, let them dry fully, and reinstall. Look at where the drain hose exits outside and make sure it isn't kinked, crushed under a deck board, or blocked by leaves, a wasp nest, or ice.
Stop there. Do not open the sealed refrigerant system, probe the electronics, or try to re-pitch the drain line yourself — these involve refrigerant handling and electrical work that, in BC, should be done by a qualified technician. Refrigerant work in particular is regulated and requires proper certification and recovery equipment.
Heat pumps and mini-splits are serviced by our parent company, CanroHeat. If your Mitsubishi unit is leaking indoors and a quick filter clean didn't fix it, call CanroHeat at 604-359-1081 and we'll get a technician out to find the real source.
What Repairs Typically Cost in Greater Vancouver
Costs vary with the cause and your specific install, so treat these as broad ranges, not quotes. A straightforward drain-line clearing and pan treatment is usually one of the more affordable visits. Replacing a failed condensate pump, correcting a poorly sloped drain line, or swapping a cracked pan sits in the mid range because it involves parts and more labour.
A refrigerant-related leak — where the coil was freezing and the system is low — is the most variable. It depends on whether there's a repairable leak in the lineset and how much refrigerant the system needs. We never guess at sealed-system pricing sight-unseen.
For an accurate, no-surprises figure for your exact situation, call CanroHeat at 604-359-1081. We'll diagnose the leak, explain what's causing it in plain language, and quote the repair before any work begins.