How to Troubleshoot & Fix Common Underfloor Heating Problems

Radiant underfloor heating systems offer some of the most efficient and comfortable heating available—but like any mechanical system, they can occasionally need attention. Whether you’re dealing with uneven heating, system pressure loss, or a full zone that won’t warm up, understanding the basics of underfloor heating repair can help you avoid costly service calls and restore comfort faster.

This guide focuses on hydronic (water-based) systems, covering common issues, how to troubleshoot them, and when it makes sense to repair versus replace. Visual diagrams and tips are included to help homeowners, contractors, and builders identify and fix problems quickly.

How Hydronic Underfloor Heating Systems Work

Hydronic radiant systems heat your space by circulating warm water through a network of tubes embedded in or below the floor. The heat radiates up, warming floors and the air above evenly.

System Components:

PEX tubing laid in loops beneath flooring
Manifold system with valves and actuators
Pump and heat source (e.g., boiler or heat pump)
Thermostats and zoning controls

Common Underfloor Heating Problems

Even well-installed systems can experience wear, installation errors, or mechanical failures over time. Here are the most frequent issues and how to troubleshoot them.

1. Uneven Heat or Cold Spots

Causes:

Air pockets in the tubing
Kinked or damaged PEX
Poor loop balancing
Sensor or thermostat issues

Fixes:

Bleed air from system via the manifold
Use an infrared camera or a heat gun to locate cold zones
Check and adjust flow rates at the manifold
Inspect and recalibrate zone thermostats

2. Zone Not Heating at All

Causes:

Actuator or zone valve failure
Pump not engaging
Thermostat disconnected or faulty

Fixes:

Test power to the thermostat
Manually open zone valves to test flow
Check pump function and verify it’s receiving power

3. System Pressure Drop

Causes:

Leaks in fittings, joints, or tubing
Expansion tank failure
Air in system causing false readings

Fixes:

Isolate loops one at a time to identify the leak
Inspect visible fittings and test pressure over 24–48 hours
Check expansion tank pressure (typically 12–15 psi)

4. Slow Heat-Up Time

Causes:

Lack of insulation under slab
High-R flooring material (e.g., carpet)
Loop design with excessive length

Fixes:

Use programmable thermostats to preheat zones
Add insulation where possible (especially in basements)
Consider supplemental insulation or upgraded panels in future retrofits

Can Tubing Be Repaired?

Yes—if the tubing has been mechanically damaged (from drilling, renovations, or excessive subfloor movement), a repair can be made.

How to Repair PEX Tubing:

Turn off the zone and depressurize the system
Cut out the damaged section
Use PEX couplings and crimp rings to install a new piece
Pressure test before re-covering

When Should You Replace a Panel?

In systems that use modular radiant panels (such as grooved wood or insulated foam boards), it’s often possible to replace just the affected area.

For example:

Panel with warped surface
Crushed aluminum layer
Panels that delaminated due to moisture exposure

A major advantage of modular systems is that flooring can be removed in one area, the panel replaced, and tubing reinstalled without affecting the entire floor.

Example Product Reference:
Panels like Radiantboard and Thermalboard from Warm Brothers Inc. are modular, grooved radiant solutions that allow for isolated repairs. Their layered design supports tubing replacement or repair without tearing up the entire floor.

Preventative Maintenance Tips

The best way to avoid costly underfloor heating repair is through proper design and preventative care:

1. Use Oxygen-Barrier PEX

Prevents corrosion in metal parts of the system.

2. Avoid Overly Long Loops

Stick to 250 ft max to ensure good flow and heat distribution.

3. Install Expansion Joints

In concrete applications, this prevents floor cracks from damaging tubing.

4. Pressure-Test Before Covering

Always perform a pressure test after tubing installation and before pouring or laying finish floors.

When to Call a Professional

You can handle many of the above checks and fixes on your own, especially if you have your system’s layout plan. But call a radiant heating professional if:

You’re losing pressure and can’t find the source
More than one zone fails at once
You need to open flooring or concrete to access tubing
Manifold valves, sensors, or controls need advanced diagnostics

Pro Tip:
If your system was professionally installed, you should have a loop map or CAD layout showing all tubing runs, loop lengths, and connections. Always refer to this first.

How WBI Supports Repair-Friendly Installations

While this post is primarily informational, it’s worth noting that Warm Brothers Inc. designs their radiant systems for long-term access and serviceability.

WBI Panel Benefits for Repair Access:

Modular board format allows for localized replacement
Grooved channels for easy tubing access and reinstallation
Aluminum-clad surface offers superior heat transfer and durability
Ideal for slab or basement installations where access may be limited

These features help reduce repair time and complexity—especially in long-term residential or light commercial projects. Learn more at wbiwarm.com.

Summary: Underfloor Heating Repairs Are Manageable with the Right Knowledge

Most issues with radiant systems, especially hydronic ones, can be resolved with a few basic troubleshooting steps. Whether you’re addressing uneven heat, cold zones, pressure loss, or tubing damage, having the right tools, layout info, and understanding of how your system works is key.

If your system uses modular panels and high-quality materials, the repair process is even more manageable.