Gurgling sounds from a sink drain have a different cause than similar sounds coming from the faucet, but in either case, it's air that is making the sounds, and the air shouldn't be there. If a faucet is gurgling, and you're on a well, and it could mean something is wrong with the pressure tank or the well itself. Whether or not you're on a well, the air could also signify a leak in some system component. Gurgling from the drain usually means a vent blockage, and that could, in turn, be caused by an obstruction in the drain.
Air in the faucet is often a temporary problem that goes away after a few minutes, and if the gurgling is confined to a single faucet, there's usually nothing to worry about. You should consider some problematic possibilities, though:
Bubbles in a Well-Fed System
If you have a well, air bubbles are something to which you need to pay attention. If you notice sediment in the water, it's a sign that the well level is low. On the other hand, if you have an older pressure tank without a bladder, air can get mixed with water inside the tank. The same thing can happen if the bladder ruptures in your newer pressure tank. Air can also enter any pipe that ruptures anywhere between the well and the building.
Bubbles in the Hot Water
If you notice air in the hot water, a potentially dangerous condition could exist at the water heater, whether or not your water is supplied by a well. It could mean the temperature is set too high. Turn off the hot water heater immediately and let the water cool down before calling a plumber or servicing the water heater yourself.
Air from Other Sources
Water softeners and filters can leak air into the water when fittings are loose or when a check valve malfunctions. If you suspect this, bypass the equipment to see if the air disappears, then service the equipment as needed. If you're on a municipal water system, you may have air at your faucet simply because work is being performed on the system. Though troublesome, it's usually nothing to worry about. The air will escape when you run the faucet.
Gurgling sounds from the drain are the result of air inside the pipes pushing or pulling on the water in the drain P-trap. You may notice the gurgling sound when someone flushes a toilet or uses an appliance that quickly drains a large amount of water, such as a washing machine. In the absence of a clear air passage -- which should be provided by a blocked vent -- this water can create suction in the pipes, which pulls on the water in the P-trap. If the sink drain is between the flowing water and the blocked vent, positive air pressure may push on the water instead. Either way, gurgling is the result.
The Plunger Approach
In some plumbing systems, a drain for one fixture may serve as a vent for another. In this configuration, which is called a wet vent, a drain obstruction can produce symptoms of poor venting. For this reason, you may be able to stop sink gurgling by or shower or bathtub drain.
Plunging the sink itself may also work. That may not completely clear the obstruction, but you should notice an improvement. If not, it's time to focus on the vents themselves.
Solutions for Blocked Vents
- The solution depends on your plumbing configuration. You may have to clear the roof vent; if it's winter, the vent may be ice-bound, and in other seasons, it may be filled with leaves.
- If the sink has a vacuum breaker vent -- sometimes called a cheater vent -- it may be malfunctioning and need to be replaced. This is most likely if the sink is in a kitchen island.
- If you can't find a way to solve the problem, the fault may be with the plumbing design, and you may need to hire a plumber to investigate.