How to Fix a Leak in the Radiator

If there is a leak in the radiator, especially this time of year, then you are going to want to fix it fast. A leaking radiator might be a DIY job if handled properly. If you are uncomfortable in any way then we highly suggest that you give a local plumber a call.

Before You Start

As you know, radiators get hot. Do not work with a hot or even warm to the touch! Give at least an hour if not more for the radiator to cool down before you even begin to find where the leak may be.

radiator valve

Find the Leak

The first step is finding the leak in your radiator. After the radiator has been turned off, and cooled down, wipe down the radiator with a towel to dry the machine. After that take a paper towel and gently tap over the whole machine. Make sure to notice when water appears on the paper towel. This is how you find a leak in your radiator.

plumber fixing a leak in the radiator

Leaks in the radiator generally come from three different sources, the valves, body, and pipe connections. This can be from corrosion, valves not being fully tightened or broken, or connections not being as secure as they should be.

Empty Your Radiator

empty radiator if there is a leak in the radiator

Most of the time before you work on a radiator, you’ll need to empty the water. Again, make sure to do it after the radiator has been turned off and cooled, as well as find the leak in the radiator. You are going to want to make sure you shut off your lockshield and thermostatic valves. You must put a towel down, and then a bucket under each valve to make sure you protect your flooring. With both valves, remove the nut that is connected to the valves. The last thing to do before tipping over the radiator gently is to take your radiator key to release any excess air.

Leak in the Valve Gland and Spindle


Inside the valves there is a metal spindle, this metal spindle is attached to a valve that has a gland nut. This gland nut is generally what causes the leak in this situation. There should be a cap on this, if there is, remove that before starting any work. Once that cap is removed all you need to do is tighten the bolt. This should stop the leaking from occurring. You can use thread tape as well on the male end of a thread. This can help create an even more water-tight seal.

Leak in the Body of the Radiator

leak in the radiator

If the leak in your radiator is in the body, it is likely as small as a pinhole. Due to the likelihood of corrosion causing this, a great temporary fix is using a sealant epoxy. This may hold for a little while, but may eventually need to get replaced. It is important to use the correct kind of sealant. Use one that is for a stand-alone radiator, not a boiler in a central heating system.

Leaks in the Pipe Connection

leak in the radiator

Most of the time this leak in the radiator is a very easy fix. It is generally just making sure the union nut is fully tightened. However, if you do that too much it can make the leak in your radiator worse as it will damage the connection. If you notice that tightening doesn’t make a difference, then you may need to replace the bolt. When you do that make sure to add thread tape to the bolt and that should provide you with a water-tight seal.

Things to Lookout For

radiator leak

Keep in mind these few signs that could signal a leak in the radiator may be happening shortly. First is a rusty radiator, rust can cause holes to appear in your radiator. Radiators usually last about ten years. After this, they can become rusty. Next is any loose or perhaps even damaged valves or connections. These will cause water to leak out the sides. Make sure you are inspecting your radiator for any leaks every couple of months.

Final Thoughts

A leak in the radiator can sometimes be fixed by a quick tightening of a bolt or connection. However sometimes a leak in the radiator needs to be fixed by a plumber, and occasionally even replaced fully. It is important to get them fixed as soon as you can, as it wastes water and can make your radiator not work properly.

Call 1-Tom-Plumber

Don’t hesitate to contact us here or call us at 1-Tom-Plumber (1-866-758-6237) if you need help with the plumbing on your radiator heating system.

1-Tom-Plumber’s certified team of plumbers and drain technicians respond immediately to any emergency plumbing, drain cleaning, or water damage problem. We also handle the excavation of underground water lines and sewer main lines. Our immediate-response team is available every day and night of the year, even on holidays.

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