Combi boilers may not be ideal for every home type, but for those with hydronic space heating, they can provide a convenient two-in-one space and water heating solution. Taking care of your space and water heating in one fell swoop sounds great, but like any investment, there are a few things to consider before going all in on a combi boiler.

At Monkey Wrench Plumbing, Heating, Air & Electric, we install combi boilers across Los Angeles County and the surrounding cities. With over 15 years of experience installing and servicing combi boilers, we’ve come across a few issues with these units in the field.

In this article, we’ll walk you through some of the most common problems with combi boilers so you can get a better idea of what you might potentially run into down the road. As a disclaimer, you may never run into some of these issues, but having this information in your back pocket can help you avoid surprises down the road.

Let’s jump in with the most common problem we see with combi boilers in the field.

Common Problems with Combi Boilers

Incorrect Installation

One of the most common issues we find in the field with combi boilers is incorrect installation. We chalk this up to the lack of qualified technicians who can install combi boilers. This type of installation is tricky because combi boilers require a technician skilled in HVAC and plumbing.

Sometimes, you may need to call out a plumbing technician and an HVAC technician to handle the installation. There are technicians skilled in both areas of expertise, but they are typically few and far between. To avoid incorrect installation, it’s in your best interest to go with an installer skilled in both trades.

But technicians aren’t the only piece of the muzzle that’s difficult to track down regarding combi boilers.

Outdated Unit and Lack of Parts

Another common problem we run into in the field is older units or discontinued ones. This pitfall is most common with some of the older Baxi units around Los Angeles County. Parts are difficult to come by for these models since Baxi only has one distributor in California, and it is based in Northern California.

In these cases, your technician will likely recommend an upgrade. Considering that combi boilers have a general lifespan of 15 years, and if your technician can’t locate parts, then it is probably time for an upgrade.

While factors like a shortage of qualified technicians and parts should be considered, let’s take a look at some of the inherent problems you may run into with a combi boiler or any tankless style water heater, for that matter.

Heat Exchanger Corrosion and Leaks

In areas with hard water, like Los Angeles County, leaks in your combi boiler’s heat exchanger are common without proper maintenance. Because Los Angeles is affected by hard water, these minerals cause scale build-up and can jeopardize your combi boiler’s efficiency. Once this happens, you can bet on a heat exchanger leak following close behind.

There are plenty of options available to help combat hard water. Any easy way to skirt this issue is with water treatment. Some types of water treatment, like water softeners, aren’t allowed in certain municipalities, so it’s always best to do a bit of research and speak with a certified technician. Annual maintenance is also key to preventing these leaks from forming altogether.

Leaks are one beast, but blockages are another. Despite the importance of preventing leaks, ensuring your unit is free from blockages will also promote a longer lifespan and greater efficiency.


Blockages are sneaky and can form in your venting or heat exchangers. The usual suspects apply here. A blockage may occur if your system has excess scale build-up, sludge, or debris.

Just as it goes with leaks, blockages can tank efficiency and lead to more serious issues down the line. These types of blockages are challenging to locate on your own, so your best course of action is to call out a technician to diagnose your combi boiler properly. You can also prevent blockages with annual maintenance.

Up to Speed on Common Combi Boiler Problems

Combi boilers aren’t without their potential downsides, as with any investment. While we’ve run through the most common problems with combi boilers we run into in the field, every home is different and can present its own set of issues. But with this knowledge, you can build a better idea of what to expect when it comes to things to look out for regarding your combi boiler’s health.

After over 15 years of installing and servicing combi boilers in the Greater Los Angeles Area, we’ve nailed down the most common issues in the region. We’ve spent years defining our service process and building out a roster of qualified technicians to install and maintain combi boilers.

If you need help with your combi boiler and live in Los Angeles County or its surrounding areas but don’t know where to start, get in touch with one of the buttons below or by scheduling an appointment through our online scheduler.

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