Low pressure taps work by remaining permanently open, allowing cold water to flow into the water heater, which then displaces the hot water upwards and out of the tap.
Here's a more detailed breakdown:
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Designed for Non-Pressurized Water Heaters: Low pressure taps are specifically designed for use with non-pressurized (or unvented) water heaters, also known as "open outlet" water heaters. These water heaters do not store hot water under pressure.
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Permanent Open Outlet: Unlike standard taps, a low-pressure tap's outlet is always open to the atmosphere. This is the key to their operation.
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How Hot Water is Delivered:
- Tap is "Off": When the tap is closed, the cold water supply is shut off. The water heater contains a reservoir of hot water at the top.
- Tap is Turned "On": Turning on the tap opens the cold water supply valve.
- Cold Water Enters the Heater: Cold water flows into the bottom of the water heater.
- Hot Water Displaced: The incoming cold water pushes the hot water already in the heater upwards.
- Hot Water Exits the Tap: The hot water is forced out of the tap's permanently open outlet.
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Why Low Pressure Taps are Necessary: Using a standard, pressure-tight tap with a non-pressurized water heater would be dangerous. Because the heater isn't designed to withstand pressure, closing a standard tap after heating the water could lead to a build-up of pressure and potentially a rupture or explosion of the water heater. The low-pressure tap's open outlet prevents this pressure build-up.
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Kitchen and Bathroom Applications: These taps are commonly found in kitchens and bathrooms where point-of-use, low-volume hot water is desired.
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Mixer Taps: Many low pressure taps are mixer taps, allowing you to blend hot and cold water to achieve your desired temperature. The cold water side functions as a standard cold water tap, while the hot water side controls the flow of cold water into the water heater, which in turn controls the flow of hot water out of the tap.
In summary, low pressure taps rely on a permanently open outlet and the principle of displacement to deliver hot water from a non-pressurized water heater, ensuring safety by preventing pressure build-up within the system.
