Section 890.1170 Potable Water Supply Tanks and Auxiliary Pressure Tanks

Section 890

Section 890.1170  Potable

Water Supply Tanks and Auxiliary Pressure Tanks

a)         Water Pressure.  When the water pressure from the public water

supply main is insufficient during periods of peak flow or due to the building

height to supply all fixtures in accordance with Section 890.1210(c), the rate

of supply shall be supplemented by a gravity tank or auxiliary pressure

(booster) system.  Auxiliary pressure systems shall not substitute for adequate

sizing of water distribution piping within the building.

b)         Support.  All water supply tanks shall be supported in

accordance with local building codes or authorities having jurisdiction.

c)         Tank Supply Inlet and Outlet.  The water supply inlet to the

tank shall have a minimum air gap of at least 6 inches.  The supply outlet

shall be a minimum of 4 inches above the bottom of the tank.

d)         Overflow For Water Supply Tanks.  Overflow pipes for gravity

tanks shall be indirectly connected to the drainage system with an air gap of

at least 6 inches.  Overflow pipes shall be full sized, unrestricted and

screened with 24-mesh per inch stainless steel or bronze screen.

e)         Size of Overflow.  Overflow drains for gravity water supply

tanks shall have an area of at least twice the size of the supply pipe.

f)         Drains.  Water supply tanks shall be provided with valved

drain lines located at their lowest point and shall discharge through an

indirect waste with an air gap of twice the diameter of the drain line.  The

drain line and valve shall have no restrictions and need not exceed 2 inches in

diameter.

g)         Gravity and Suction Tanks.  Tanks used for potable water supply

or only to supply fire-fighting equipment shall be equipped with tight,

overlapping covers that are rodent and insect proof

nd shall discharge through an

indirect waste with an air gap of twice the diameter of the drain line.  The

drain line and valve shall have no restrictions and need not exceed 2 inches in

diameter.

g)         Gravity and Suction Tanks.  Tanks used for potable water supply

or only to supply fire-fighting equipment shall be equipped with tight,

overlapping covers that are rodent and insect proof.  The tanks shall be vented

with a return bend (turned down) pipe having an area at least ½ the area of the

tank outlet pipe, and the vent opening shall be covered with a stainless steel

or bronze screen of at least 24-mesh per inch.

h)         Pressure Tanks.  Pressure tanks used for supplying water to

the water distribution system, or only to supply standpipes for fire equipment,

shall be equipped with a vacuum relief valve located on top of the tank.  An

air inlet of this device shall be covered with a stainless steel or bronze

screen of at least 24-mesh per inch.  (See Section 890.1230(f).)