There are two types of hot water loss. There is an overall service issue, usually with the water heater, that results in no hot water or greatly reduced amounts of hot water at every tap in the home. The other type is point-of-use loss, which means only a single faucet, shower head, or tap is without hot water. Troubleshooting point-of-use hot water loss can be a bit more challenging.
Signs of Point-of-Use Hot Water Loss
The first task is to determine whether it is point-of-use loss or an issue with the entire system. Check each hot water tap individually at a time when you know that the hot water tank should be full and heated. Let each tap run for several minutes to see if the water heats up. If it does at some of the taps, then it is likely a point-of-use problem.
Point of use issues generally only affect a single tap, but in some cases, they may affect all taps connected to a single hot water supply line. For example, there may be no hot water to the bathroom sink or the shower if both are connected into the same hot water supply line. Further, there may be a complete loss of hot water or just a reduced flow of hot water, depending on the cause.
Common Causes of No Hot Water
The most common cause of point-of-use loss is at the water supply line. It could be as simple as the main valve on the line is closed and it needs to be opened or further opened, if there is reduced hot water flow. There could also be a leak in the hot water supply line that is preventing the water from making its way to the tap. Leaks can result in complete or partial hot water loss. Sedimentation and limescale is another common problem, as it can block the line.
Issues with the tap itself could be at fault. For example, in the shower there is a diverter that diverts water from the tub faucet to the shower head. If you have hot water in the tub but not the shower, then this diverter is to blame. There is also a diverter in every single handle faucet tap that allows you to adjust the amount of hot and cold flowing from the faucet. If this diverter fails, you won't be able to get hot water from the tap.
Contact a plumber if you are suffering a loss of hot water at a single faucet.