This issue can arise for a number of reasons. If you have a long house with the water heater at one end, sometimes it simply takes a long time for water to move across. One common reason is if you have updated the faucets in your home. Modern faucets are designed to conserve water and so it takes longer to purge the cold water from your pipes. Where your old faucet took 30 seconds to bring hot water, the new faucet takes 1 minute 30 seconds or longer.
If this is a sudden change, and you used to have hot water instantly, it is possibly you already had a system of this sort, but that the pump has failed.
This topic assumes that if you are patient, you do eventually get truly hot water.
QUICK FIX:
If this problem is occurring in your bathroom, the simplest way to speed up the process is to turn on the hot water in your tub. The tub is able to move water at a higher volume, which more quickly purges the cold water from your line. (The same total volume is moved, it is simply moving faster.) If you are concerned about pouring the water down the drain, keep a watering can or a bucket handy for watering your plants.
If the problem is in the kitchen, there is not usually a high volume fixture handy. In this case, see the repair solution.
REPAIR:
Hot water circulation systems have been designed to improve this flow problem. It is a two part system consisting of a pump at the hot water heater and a thermostat under the affected fixture or fixtures. This connection creates a loop in the pipe which keeps the water in the pipes warm, and allows cold water to return to the hot water heater to be reheated. No water is wasted in this system, and it does not affect your water meter usage.
Some newer homes were built with a “3-pipe” system, to allow for this circulation from initial construction. If you used to have instantly hot water and suddenly it has stopped, most likely the pump has failed and needs to be replaced.
MAINTENANCE:
The most important piece of maintenance related to these systems is making sure that the cartridges in your faucets are replaced as they wear out. The pump creates a slight pressure imbalance between the hot and cold water lines, which allows circulation to happen. As cartridges wear out, they may allow the pressure to bleed across, which will allow the hot water to circulate too much, and even the cold lines will become hot from the circulation.
One effect of installing these systems can be discovering that cartridges are already beginning to fail. If that is the case, additional maintenance in the home may be required to allow for proper functioning of the pump.
Occasionally the thermostats will fail, and stick in either a fully open or fully closed position. When this happens, the part needs to be replaced.