Toilets that continuously run water are an annoyance but an easily fixed problem. Gurgling toilets might catch you off-guard and leave you uncertain of what would cause such a problem and how to fix it. The cause essentially comes down to the fact that your home's plumbing operates as a vent-drain system that requires water pressure to move in certain directions in order to keep the system in balance.
A gurgling toilet is a sign that the vent-drain system has become imbalanced. There are two main reasons this can happen and the fixes should both involve a plumber unless you have a lot of experience in the area.
Blocked Roof Vent
Your home's plumbing system has vent pipes that stick out through your roof. The pipes exist to both let out any potential sewage gases trying to come up through your waste lines and to provide air pressure to help wastewater flow downwards and out the sewage system. If the vent becomes blocked, the air pressure is minimized or outright removed and the wastewater doesn't drain as efficiently. Thus, when you flush your toilet and create new wastewater, the toilet gurgles because the leaving water essentially has a hiccup as it tries to leave.
Plumbing vents in your roof can become blocked by the elements – namely, ice and snow buildups – or by debris trapped in the top section of pipe. Call a plumber to come out and clean the plumbing vents because climbing up onto your roof is risky if you don't have the experience or proper equipment.
Your plumber might also offer advice on how to prevent the problem from happening in the future such as wrapping a frozen pipe in thermal tape or installing a grated vent cover to prevent debris from becoming lodged in the pipe.
Plugged Sewer Line or Septic Tank
If your roof vents are clear, the imbalance could be happening at the other end of the system where the wastewater enters either the sewer line or your septic tank. The blockage causes the wastewater to start to buildup, which can cause the gurgling when you flush the toilet.
If your home empties into a city sewage system, call in a plumber to check the lines and clear any blockages. Sewage is hazardous material so you don't want to perform line checks on your own unless you have the experience and safety equipment.
Does your home have a septic tank? The tank could be blocked or the levels are simply full. Call out your septic company to have the tank check and emptied, if needed.