Plan Review for Storage Tanks

What types of tanks are reviewed as finished water storage tanks?

• Water towers
• Standpipes
• Ground reservoirs
• Clearwells

In addition, plans for backwash reclaim tanks are reviewed under the design standards for finished water storage for isolation distance purposes.

What do I need to include in a submittal of storage tank plans and specifications?

• Capacity of the tank.
• A scaled site plan showing the tank location, utilities, and site grading.
• A profile view drawing of the tank showing overflow piping, inlet/outlet piping, baffles, access hatches, tank vent, and dimensions.
• A plan view drawing of the tank roof showing access hatches and vent.
• Detail drawings of access hatches, vent design, and overflow discharge.
• Manufacturers name and product name/number for tank coatings.  The interior tank coating must be ANSI/NSF Standard 61 approved and listed.
• Procedures for the tank construction and disinfection.
• Geotechnical information including any groundwater levels for below grade reservoirs.

How far away does a below grade tank need to be from buried sewer?

A minimum of 50 feet measured horizontally is required between any part of the tank and the outer surface of the sewer pipe.  If this separation cannot be met for gravity sewer, the Minnesota Department of Health may allow the below grade tank to be located less than 50 feet from the sewer if the sewer pipe is provided with secondary containment or if additional measures of protection are provided for the finished water tank.

What are the requirements for roof access hatches?

• At least two access hatches must be provided above the high water level to the wet portion of the tank interior, where space permits.  The vent does not count as an access hatch.
• For above grade tanks, the top of the hatch must extend 4-6 inches above the tank surface.
• For below grade and partially buried tanks, the top of the hatch must extend 24-36 inches above the top of the tank or surrounding grade, whichever is higher.
• The hatch cover must be hinged, lockable, solid, and watertight.  It must overlap the framed opening and extend down around the frame by at least 2 inches.

Can I install a mixer in the tank?

Yes.  However, the mixer must meet ANSI/NSF Standard 61 standards or be constructed of materials and equipment that is ANSI/NSF Standard 61 listed.