Understanding And Fixing The Cold Water Sandwich

Most sandwiches are delicious, but the "cold water sandwich" you might experience when you turn on the hot water in the morning will not leave you with the satisfaction of a nice BLT. The cold water sandwich effect occurs when you have a tankless water heater. Since water is heated "on demand", residual water pipes in the pipes can still be hot from the last person who used the hot water. You hop in the shower with the water deceptively warm, only to have it change to ice-cold for a few seconds before it starts to warm up as the heater begins to work. Is there anything you can do to prevent the cold water sandwich?

Change your heater.

There are two types of tankless water heaters: gas and electric. Electric heaters tend toward to the cold water issue issue more frequently than heaters that use gas. Gas heat is immediate, while electric heaters take a while to warm up and cool down, extending the length of cold water spell. 

You can also get tankless heaters that still heat for a few minutes after turning off the tap, so hot water still stays warm for the next person to turn on the tap unless the water hasn't been run for a while; if someone is using the tap to wash a dish downstairs before someone turns on the shower upstairs, there won't be as great of a temperature fluctuation. 

Maintain good water pressure.

If water moves sluggishly through the pipes, the heater will not kick on as quickly or heat the water as evenly. Sometimes, the hardness of your water and the level of minerals can affect water pressure. For example, if you have calcium deposits on your tap, water will not come out as easily, which means the cold water sandwich will last longer, instead of emptying efficiently through the tap. Sediment can also build up in the pipes, especially if you have water with high sulfur or iron content. The best way to avoid pressure problems from hard water is to install a water softener or similar filtration system that removes minerals from your water supply. 

If all of your taps are cleaned and clear and you still have poor pressure, it's best to call a plumber to assess why you have lower-than-normal water pressure. Other common causes for low pressure include corroding pipes and small leaks. Small leaks will mean that you have a constant flow of warm and cold water through the pipes, resulting in the sandwich problem much more often than normal. 

Install a reserve tank.

Tankless water heaters are great for small space designs and for small homes because they can be more energy efficient. However, if you have a large home, you may want to install two sources for hot water. You might have a small storage-style hot water tank installed for showers and baths but have the kitchen hooked up to a tankless heater to help you save on water heating and usage. Storage style heaters will ensure there is always hot water present at the beginning of a shower, and it won't matter what someone in the kitchen is doing with the tap.

You can also use two tankless heaters for different areas of the house. If one or two bathrooms are supplied with one heater and the kitchen and laundry are supplied with another, there will be less cross-usage, which will result in fewer sandwich incidents.

Using the above tips, you can reduce the unpleasant flash of cold water that sometimes comes with tankless water heaters. For more information on fixing your water heater problems or improving your water pressure, contact a plumber from a company like Salinas & Sons Rooter Service


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