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On Joining PVC Pipes

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There are usually many many pipes in a building, and because PVC is cheap and (mostly) long-lasting, it is going to be used for quite a portion of it. For example, sanitary pipes are mostly PVC, rainwater pipes could also be PVC. Here is how PVC pipes are joined together: To join 2 PVC pipe parts together, one part needs to have a larger circumference than the other so that a portion of one pipe could fit into the other one snugly (a male and female joint). When joining, the joining edge of both pieces are first thoroughly cleaned of debris, then applied with a primer. The primer, a viscous liquid, is coated around the area intended to be joined so that it "bites" the micro-surface of the edge so that it becomes a little more rough. Subsequently, when this primer sets a little (in probably less than a minute), a second liquid, the glue, the applied over the area where the primer has been applied. Then, the pipes are immediately joined and a half twist is done to ensure the g...

On Concrete Honeycomb

After concrete is cast, honeycomb may appear on the surface or inside the concrete structure. These honeycomb structures are hollow parts of the structure where concrete has not reached during the casting process. Reasons for this are associated mostly with poor workmanship during casting, such as: Inadequate and improper vibration when filling the concrete in Big or chunky aggregates that prevent the flow of concrete Concrete mixer that is too dry/ too stiff To rectify concrete honeycombing, it is necessary to use this material called "pressure grout" rather than conventional cement. This is because when pressure grout is applied, the pressure it has when it is injected will make it spread out across the honeycomb area and fill up all the holes effectively. If conventional cement is applied, it will only cover up the visible portions of holes on the surface, leaving honeycomb holes further in the cast portions left unfilled. When this occurs, the effectiveness of th...

On Components of a Fire Fighting System

Dry Riser A riser that is usually dry, but could be filled with water pumped in from a fire truck when required to fight fire The riser connects to a landing valve on each floor In Singapore, this usually applies to buildings between 10m - 60m in habitable height, and any basements Wet Riser: A riser that is always kept full of water to fight fire. Usually required for high rise buildings in which the floors are too high for the fire brigade to pump water up efficiently when necessary The riser connects to a landing valve on each floor In Singapore, this usually applies to buildings exceeding 60m in habitable height Breeching Inlet: A breeching inlet is a connection point that feeds water from a fire truck up into a dry riser It is usually located on the ground floor; when not on the ground floor, it is on the main floor accessible by the fire truck Hydrant: A valve point on the ground floor where fire trucks and fire men could tap water from Landing Valv...