Why Is My Heat Pump Spitting Water?

First thing to know: water pooling outside your outdoor unit is normal. Water running down your hallway is not. Here’s the difference and what you need to do about it.

Normal vs. Problem: What You’re Looking At

Heat pumps extract moisture from the air as they heat or cool your home. That moisture condenses on the cold evaporator coil and becomes liquid water. The system is designed to collect this water in a drain pan and send it outside through a drain line. When everything works, nobody notices. When something breaks, you get water damage.

Outside Your House (Usually Fine)

In heating mode, the outdoor unit removes heat from outside air, which removes moisture too. Water drips onto the ground under your unit. Completely normal. The same thing happens inside during summer cooling – water drips somewhere outside.

You only have a genuine problem outside if you’re seeing excessive water, like someone’s running a tap next to your unit. That might signal frozen coils (which can happen in very cold weather) or something else broken. A normal amount dripping? Ignore it.

Inside Your House (Needs Attention)

Water coming from your indoor unit is different. This unit sits on your wall or ceiling. It’s supposed to pull condensation into a pan, then down a drain line to outside. When that process breaks, water leaks into your home.

This matters because standing water leads to mold. Mold damages your home’s structure and air quality. Water near electrical components creates short circuits or worse.

What’s Actually Causing It

The most common issue by far: a clogged drain line. This happens to about 90% of indoor leaks. Your condensate drain line gets blocked with dirt, algae buildup, spider webs, or random debris. Water backs up into the pan and leaks out the sides or bottom.

You might clear it yourself. The drain line is usually a small plastic pipe running from your air handler toward outside. If you can see where it exits the house, you can sometimes blow it out or use a plumbing snake. If you’re not comfortable doing this, call someone. It’s not expensive but you don’t want to accidentally damage anything.

Other causes include a cracked or rusted drain pan. These corrode over time, especially when water sits in them for ages. The pan might also be misaligned if your air handler shifted. Either way, someone needs to replace or realign it.

If your air filter is completely clogged, airflow over the evaporator coil gets restricted. The coil gets too cold and freezes. When it thaws, all that water melts and backs up the drain. You’ll often see this in winter during heating or after installing a new filter backwards.

Low refrigerant creates the same problem. If you have a refrigerant leak, the system can’t work properly and the coil freezes. You’d typically notice your power bill jumping significantly along with the water issue.

Causes and Severity Comparison

Cause	Where Water Appears	Severity	DIY Fix?	Cost to Repair
Clogged drain line	Indoor pan overflows	Medium	Sometimes	$50–200
Dirty air filter	Water backup after thaw	Medium	Yes (simple)	$15–40
Cracked drain pan	Constant pooling below unit	High	No	$200–400
Frozen evaporator coil	Water during/after thaw	High	No	$300–800
Low refrigerant	Water + weak heating/cooling	High	No	$400–1000+
Misaligned air handler	Uneven pooling in drain pan	Medium	No	$150–300

What You Can Actually Check

1. Start with the filter. Replace it if it’s visibly dirty. This solves the water problem more often than you’d think. A clean filter costs about 20 dollars and takes five minutes.
2. Look at the drain line. Walk outside and find where it exits your house. Clear away leaves or debris around the opening. If it’s obviously blocked, that’s your problem right there.
3. Check under the indoor unit. Is there a visible puddle forming? Look at the walls around it for water damage or mold spots. If you see mold, moisture has been building up for a while.
4. Listen to the unit. Weird gurgling sounds usually mean water’s pooling inside the pan and can’t drain.

When to Call a Professional

If your filter’s clean and the drain line is clear but water’s still coming out, call someone. Don’t ignore it hoping it fixes itself.

If you notice your power bill jumping up along with the water issue, you might have a refrigerant leak. That needs professional equipment to diagnose and fix.

Frozen coils look like ice caked onto your outdoor unit or around your indoor coils. That’s not a DIY fix.

How to Stop It Happening Again

• Keep your air filter clean. Every one to two months depending on how much you use the system. This is the reason installers get about half their water leak calls. Regular filter maintenance prevents frozen coils, which prevents backup water.
• Keep your drain line clear. Pour a little vinegar down it every few months to prevent algae buildup. While you’re at it, don’t let leaves and dirt pile up around your outdoor unit. That debris works its way into your drain pan.
• Get your system serviced annually. Before heating season starts, someone should come check the whole thing. They’ll check the drain pan, clear the line, check refrigerant levels, and look at the condensate pump. This catches problems before they become water-on-your-floor problems.

We recommend servicing at least once a year, with some households (those with pets, coastal environments, or heavy use) benefiting from twice-yearly checks.

Maintenance Checklist

Here’s what you should do between professional visits:

• Check your air filter monthly; clean or replace when dirty
• Clear debris away from the outdoor unit
• Walk around outside and look where your drain line exits; ensure it’s not blocked
• Listen to the unit for unusual sounds
• Schedule professional service before heating season (autumn) and cooling season (spring) if possible

Frequently Asked Questions (FAQs)

If my indoor unit is leaking, will it damage my electrical wiring or cause a safety hazard?

Potentially, yes. Water near electrical components can cause short circuits or create shock hazards. If you see water actively pooling near wiring, switches, or electrical connections, turn off the unit immediately and call a professional. Don’t attempt to fix it yourself. Water and electricity are a serious combination.

How long can I safely leave a leaking heat pump running before it causes permanent damage?

Not long. Standing water inside your home creates mold within 24-48 hours in humid conditions. Mold damages drywall, insulation, and air quality. The longer water sits in the drain pan, the more corrosion happens to the pan itself. If you’ve identified a leak, get it fixed within a few days at most.

Can I pour water down my drain line myself to clear it, or do I need special equipment?

You can try flushing it with vinegar or hot water to prevent algae buildup, but if it’s already clogged, vinegar alone won’t clear a serious blockage. A plumbing snake or wet/dry vacuum works better, but if you’re not confident, it’s worth the $50-200 to have a professional clear it properly rather than risk pushing the clog deeper or damaging the line.

If I get the drain line cleared and it clogs again in a few weeks, does that mean there’s a deeper problem?

Possibly. Repeated clogs in a short timeframe can indicate the drain line is poorly installed (wrong angle, trapped debris), algae is growing aggressively in the line, or water damage elsewhere is sending debris into the system. A professional inspection would identify whether you need a line replacement or if something else is contributing to the clogs.

My heat pump was working fine and suddenly started leaking – could this be caused by recent weather changes?

Yes. Very cold weather can freeze evaporator coils if airflow is restricted (like a clogged filter). Heavy rain or humidity can increase condensation production. Seasonal transitions (moving from heating to cooling mode) can stress the system. Check your filter first – it’s the most common culprit when leaks suddenly appear after your system’s been running fine.

Bottom Line

Water outside is fine. Water inside is not.

Start with the filter and check the drain line. If that doesn’t sort it, call Varcoe. We’ll figure out what’s going on and fix it. Most indoor water leaks take about an hour to diagnose and usually less to fix if it’s just a clogged drain or dirty filter.

Ring 0800 088 888 and we’ll get you sorted.