New Hampshire Code of Administrative Rules
Env - Department of Environmental Services
Subtitle Env-Dw - Drinking Water Programs
Chapter Env-Dw 400 - PUBLIC WATER SYSTEM CLASSIFICATION AND DESIGN
Part Env-Dw 405 - DESIGN STANDARDS FOR SMALL COMMUNITY WATER SYSTEMS
Section Env-Dw 405.18 - Sizing of Storage Tanks

Universal Citation: NH Admin Rules Env-Dw 405.18

Current through Register No. 13, March 27, 2025

(a) The criteria specified in this section shall apply to small community water systems and to those NTNC water systems whose reliability is directly important to public health as specified in Env-Dw 405.02(g).

(b) The required atmospheric water storage capacity for a water system with only one well shall be based on the safe yield of the well and the water system's design flow, as specified in Table 403-3 below:

Table 405-3: Requirement for Atmospheric Water Storage Capacity

For Water Systems That Have Only One Source

Groundwater Source Capacity Atmospheric water storage capacity required
Peak flow 50 percent of design flow
2.5 times the design flow 75 percent of design flow
2.0 times the design flow 100 percent of design flow
Less than 2.0 times the design flow Not acceptable

(c) The required atmospheric water storage capacity for a water system with more than one well shall be based on the safe yields of the wells and the water system's design flow, as specified in Table 403-4 below :

Table 405-4: Requirement for Atmospheric Water Storage Capacity

For Water Systems That Have More Than One Source

Minimum groundwater source capacity with largest producing well out-of-service Atmospheric water storage capacity required
Peak flow none required
2.5 times the design flow 25 percent of design flow
1.5 times the design flow 50 percent of design flow
Design flow 75 percent of design flow
Less than design flow 100 percent of design flow

(d) The required hydropneumatic storage capacity shall be 10 percent of total design flow .

(e) Pre-charged pressure storage tanks shall be accepted on an equivalent gross volume basis to conventional hydropneumatic storage. No more than 6 tanks of the pre-charged pressure type shall be permitted.

(See Revision Note at part heading for Env-Dw 405) #10612, eff 6-1-14

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