Water Closet Flush Tanks

There are two designs of flush available for water closets.



Gravity operated flush tank


Pressure Assisted Flush Tank (Joke!)


Handle Assembly


Handle assemblies are not adjustable. They are held in place with a retaining nut. Thread pattern on most of the handles assemblies is of  a left-hand pattern. Some of them are manufactured specifically for a particular design of water closet. Clearly when an assembly of this kind if to be replaced it must be replaced with the correct type if is to function satisfactory.


Component Parts


Flash Valves


Flapper


Overflow Tube



Float Valve


Hush Tube


Refill Tube


Tank Lining


Float Valve Adjustments

Many float valves come equipped with two screws on the top of the valve.

The screw nearest to the center of the float valve adjusts the flow rate.

The outer screw adjusts the water level.


Backflow Prevention

When the hush tube directs the incoming water supply below the water level it does it trough a submerged inlet. This is considered to be a cross connection between the potable water supply and the drainage system, and there must be protection against the possibility of backflow. Part 7 requires that float valves must be provided with a back-siphonage backflow preventer.


7.6.2.3.(7)

Tank type water closet valves shall be provided with a back-siphonage preventer in conformance with Sentence 7.2.10.10.(2).


7.2.10.10.(2)

Back-siphonage preventers for tank type water closets shall be certified to CAN/CSA-B125, "Plumbing Fittings".


Replacement Fixtures

7.6.4.2.(2)

The flush cycle for each fixture that is a water closet or urinal and that is installed as a replacement for a fixture in a building that existed before the 1st day of January 1996 shall not exceed the maximum flush cycle listed for that fixture in Table 7.6.4.2.A (13.25 letres for  a water closet of both tank type and direct flush).


New Installations

7.6.4.2.(3)

Except as provided in Sentence (2) the flush cycle for each fixture that is a water closet or urinal shall not exceed the maximum flush cycle  listed for that fixture in Table 7.6.4.2.B (6 litres for both types of flush tanks).



Low Flush Water Closet


Pressure Assisted Water Closet Tanks




"Pressurized-tank"("PT"), "Pressure-assisted," or "Flushometer-tank" toilets look like regular gravity-flush (i.e., tank-and-bowl) toilets, but the usual porcelain tank contains a metal or plastic tank which holds water under pressure, pressurized by the building's own water pressure. When flushed, the pressurized water provides a rapid and powerful flush. The trapway (channel which carries waste from the bowl down to the waste line) in a PT toilet is just as large as the trapway in a 3.5 or 5-gallon toilet, thereby virtually eliminating the problem of clogs.

Pressure-assist toilets require a minimum water pressure of 25-40 psi to operate well.

One benefit of a power-assist flush is that the water is contained inside the pressure tank, which is inside the china toilet tank. That insulation results in little or no tank sweating. Drawbacks include noise and price: Power assist generally adds $ 100 or so to the cost of a toilet.

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