Why is my Solar Hot Water System Panel Leaking?

If you’ve spotted water dripping from your solar hot water system or seen a suspicious leak around the pipes leading to your solar panels, you’re not alone. During the colder months in Melbourne we get many calls from homeowners asking, ‘Why is my solar hot water panel leaking?’. The answer often points to a clever little device designed to protect your system — the frost protection valve.

How Do Frost Protection Valves Work?

Frost protection valves (also called FPVs or anti-freeze valves) are an important component of many solar hot water systems. Their job is to protect your system’s solar collectors (panels) and pipework from freezing on icy winter mornings.

Here’s how they work:

When temperatures near the valve drop below 3–4°C, the frost valve automatically opens to allow a small amount of water to drip out.

This slow release of water prevents the pipes and solar panel system from freezing and expanding — which could otherwise lead to cracked pipes or burst collectors.

Once the temperature rises again, the valve automatically closes and normal operation resumes.

It’s a simple yet brilliant bit of engineering — but because it’s doing its job, it can look like a solar panel leak, leading many homeowners to worry unnecessarily.

Why Is My Solar Hot Water Panel Leaking?

In many cases, that leak isn’t a fault — it’s just the frost protection valve doing exactly what it’s meant to.

However, if you’re seeing excessive dripping, leaks outside of cold mornings, an excessive water bill or water spraying rather than dripping, then something could be wrong.

Here are a few common causes:

Faulty Frost Protection Valve: These valves can fail with age, especially after a few tough winters. If the valve is stuck open, it may constantly leak.

Damaged Seals or Threads: Over time, the rubber components in the valve can perish, causing leaks even when it’s not freezing.

Incorrect Installation Position: If the valve is installed upside down or at the wrong angle, it may not work properly — or at all.

Cracked Pipework or Solar Collector: If freezing has occurred (possibly due to a faulty frost valve), it may result in a leak directly from your solar hot water panel or nearby copper piping.

Solar Hot Water Leaking? Don’t Panic — Check These First

If you’ve noticed a solar leak, here are a few DIY checks you can safely perform:

Is it freezing outside? If so, and the leak is just a gentle drip — it could just be the frost valve doing its job.

Does the leak stop later in the day? If yes, again — that’s normal.

Is the leak constant, heavy, or spraying? It’s time to call a licensed plumber.

Preventing Frost-Related Solar Panel Leaks

While you can’t stop Melbourne’s frosty mornings, you can reduce the risk of winter damage:

Regular Servicing: Have your solar hot water system serviced every few years, including a check of your frost protection valves.

Correct Installation: Ensure your system is installed by a licensed plumber who understands Victorian frost zones and solar system best practices.

Replace Faulty Valves Promptly: Don’t ignore a constantly leaking valve — it’s not only wasting water but may also lead to long-term damage.

Need Help with a Leaking Solar Panel or Frost Protection Valve in Melbourne?

At McCarthy Plumbing Group, we’re no strangers to frosty mornings and solar hot water leaks. Our licensed and qualified plumbers are experienced in diagnosing, replacing, and repairing frost protection valves, and we offer quick, reliable service across Melbourne’s west and beyond.

Whether you’re unsure about a leak, need a new frost valve, or want to get your solar system winter-ready, we’re here to help. Call us on 03 9931 0905.