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Backflow prevention device. The simplest, most reliable way to provide backflow prevention is to provide an air gap.An air gap is simply an open vertical space between any device that connects to a plumbing system (like a valve or faucet) and any place where contaminated water can collect or pool.
In the U.S., every plumbing fixture must also be coupled to the system's vent piping. [1] Without a vent, negative pressure can slow the flow of water leaving the system, resulting in clogs, or cause siphonage to empty a trap. The high point of the vent system (the top of its "soil stack") must be open to the exterior at atmospheric pressure.
The visible water surface in a toilet is the top of the trap's water seal. Each fixture drain, with exceptions, must be vented so that negative air pressure in the drain cannot siphon the trap dry, to prevent positive air pressure in the sewer from forcing gases past the water seal, and to prevent explosive sewer gas buildup.
A crack arrestor (otherwise known as a rip-stop doubler) is a structural engineering device. Being typically shaped into ring or strip, and composed of a strong material, it serves to contain stress corrosion cracking or fatigue cracking, helping to prevent the catastrophic failure of a device.
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A Allocation of costs is the transfer of costs from one cost item to one or more other cost items. Allowance - a value in an estimate to cover the cost of known but not yet fully defined work. As-sold estimate - the estimate which matches the agreed items and price for the project scope. B Basis of estimate (BOE) - a document which describes the scope basis, pricing basis, methods ...
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