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How to fix a radiant floor leak

We'll check the manifold and above-floor connections, and tell you when to call a plumber for slab leaks.

How-to · Home plumbing
30–60 min
What you'll need
  • Wrench set
  • Replacement valve or fitting (if needed)
  • Towels

At a glance

  • Check the manifold and above-floor connections first—those are usually DIY.
  • A leak in the manifold, valves, or fittings can often be fixed by tightening or replacing.
  • A leak in the tubing under the floor is almost always a job for a plumber.
  • Use a thermal camera or moisture meter to help locate leaks when possible.
  • Call a plumber if the leak is in the slab or under the floor.
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Choose the option that matches what you see. You can jump straight to that section.

Steps

Goal: Shut off the system, check the manifold, fix above-floor leaks, and know when to call a plumber.

  • Shut off the radiant floor system and relieve pressure.
  • Good: System is off and pressure is relieved. Proceed to Check manifold.
  • Bad: Cannot shut off—call a plumber.

Check manifold

Goal: Inspect the manifold and above-floor connections for leaks.

  • Dry the area. Turn the system on briefly and watch for drips at the manifold, valves, and fittings.
  • Good: You see the leak at a connection. Proceed to Tighten fittings.
  • Bad: No visible leak but pressure drops—likely a slab leak. Call a plumber.

Tighten fittings

Goal: Stop leaks at manifold or valve connections.

  • Shut off the system. Use a wrench to snug loose fittings—do not over-tighten. Turn the system back on and check.
  • Good: No drips at the fittings.
  • Bad: Leak is in the tubing under the floor—call a plumber.

When to get help

Call a plumber if:

  • The leak is in the tubing under the floor (slab or subfloor).
  • The pressure drops and you cannot find the leak.
  • You are not comfortable working on the system.

Radiant floor repair under the slab requires specialized equipment.

Verification

  • No drips at the manifold, valves, or above-floor connections when the system runs.
  • System pressure holds steady.
  • No wet or warm spots on the floor.

Reviewed by Blackbox Atlas

Frequently asked questions

Why would a radiant floor leak?
Common causes: loose fittings at the manifold, a failed valve or connection, or a puncture or corrosion in the tubing under the floor. Manifold leaks are fixable; slab leaks need a plumber.
Can I fix a radiant floor leak myself?
Yes, for leaks at the manifold, valves, or above-floor connections. Shut off the system first. If the leak is in the tubing under the floor, call a plumber—access requires cutting the floor.
When should I call a plumber for a radiant floor leak?
Call a plumber if the leak is in the slab or under the floor, the pressure drops and you cannot find the leak, or you are not comfortable. Radiant floor repair often requires specialized tools.

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