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As these need to operate in any orientation, they use a different mechanism rather than a float. The hygroscopic vent system uses hygroscopic cellulose fibre discs. [7] These are small discs of material that expand when wet and shrink if warm and dry. A dry valve acts as an air vent until a dribble of water passes through it and swells the ...
Also, a tap (or automatic vent valve) can be installed to let the gas out. Air lock problems often occur when one is trying to recommission a system after it has been deliberately (for servicing) or accidentally emptied. Take, for example, a central heating system using a circulating pump to pump water through radiators
A sewer pipe is normally at neutral air pressure compared to the surrounding atmosphere.When a column of waste water flows through a pipe, it compresses air ahead of it in the system, creating a positive pressure that must be released so it does not push back on the waste stream and downstream traps, slow drainage, and induce potential clogs.
Sealed systems offer an alternative to open-vent systems, in which steam can escape from the system, and gets replaced from the building's water supply via a feed and central storage system. Heating systems in the United Kingdom and in other parts of Europe commonly combine the needs of space heating with domestic hot-water heating.
In the United States, plumbing codes usually provide strict limitations on how far a trap may be located from the nearest vent stack. When a vent cannot be provided, an air admittance valve may be used instead. These devices avoid negative pressure in the drain pipe by venting room air into the drain pipe (behind the trap).
Kitchens and bathrooms typically have mechanical exhausts to control odors and sometimes humidity. Factors in the design of such systems include the flow rate (which is a function of the fan speed and exhaust vent size) and noise level. Direct drive fans are available for many applications and can reduce maintenance needs.
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Modern boilers discharge bottom blowdown to a blowoff tank where the blowdown can flash and vent steam upwards without entraining water which might cause burns. A pipe near the bottom of the blowoff tank maintains a water level below the blowdown entry point and allows cooler water remaining from earlier blowdown events to drain from the tank ...