Is there a gas leak?

Hello friends, welcome back to Happi Plumbing Channel.

Here’s an interesting case we’d like to share with everyone today.

The customer called because she believed there was a gas leak in her home. She said her CO alarm had gone off several times, the fire department had responded three times, and the gas company had shut off the gas supply, telling her it was too dangerous to restore service until the problem was fixed. 

The customer was convinced the leak was in the mechanical room where the furnace and water heater were located. When we arrived, we found that the gas supply valves to both appliances had already been turned off.

We started by performing a gas meter leak test. We turned on the main gas valve, took a photo of the gas meter reading, and planned to compare it again after about 20 minutes.

While waiting, we used a combustible gas detector and leak detection solution to inspect the system. We opened the gas supply valves to the furnace and water heater and carefully checked every gas connection and fitting. The gas detector found no leaks, and the leak detection solution produced no bubbles at any joint.

To be thorough, we expanded the inspection to include the gas regulator vent and every fitting upstream of the appliance shutoff valves. Still, there was absolutely no sign of a gas leak.

After more than 20 minutes, we returned to the gas meter. The reading had not changed at all, confirming that there was no gas consumption or leakage. At that point, we were confident there was no natural gas leak.

However, the customer continued insisting there was a gas leak. We then took a closer look at the gas company’s danger tag and noticed it mentioned 6 ppm of carbon monoxide (CO). That led us to suspect the problem was actually related to the water heater’s combustion or venting system rather than a gas leak.

After lighting the water heater’s pilot, we could immediately feel warm exhaust escaping from the draft hood. To demonstrate it to the customer, we held a piece of toilet paper near the hood, and it was clearly pushed by the escaping flue gases. This confirmed that the CO was spilling from the water heater’s vent hood because the venting system was blocked—not because of a gas leak.

At that point, it was clear that the issue required an HVAC contractor rather than a plumber.

In the end, we found the real problem. The customer will have an HVAC company repair the venting system. Before leaving, we shut off the water heater and closed all the gas valves to ensure the home remained safe.

The customer was extremely relieved and happy that we were able to identify the actual cause of the problem.

https://youtu.be/tMuzZ2ioM6E?is=Ff4OWMU94_EiC-se