Procedures for Flow Testing Hydrants

© 2001 Capt. Willis Lamm, Water Supply Officer, Moraga-Orinda (CA) Fire District

Regular hydrant testing is a significant component of the district's water supply program. Water systems are constantly being impacted by improvements, deterioration, changes in usage, and even water district maintenance activities which may affect zone valve settings. As a result it is important to periodically test all fire hydrants to determine what their capabilities would be in an emergency.

In addition to determining fire flows, testing can uncover a number of mechanical problems from valves that don't operate properly to leaks and even pump damaging debris flowing from hydrants. It is imperative that we discover problems and get them repaired before the hydrant is needed in an emergency.

Flow test data also provides necessary field information so that water service planners and the Fire Prevention Bureau can accurately estimate the capabilities of water mains. Water main and hydrant flow capabilities impact decisions as to what fire protection and fire resistance features are required for new developments and where priorities should be placed with respect to upgrading older, smaller water mains.

It is the objective of the district's Water Supply Program to test 1/3 of the district's hydrants each year (in addition to annual service inspections of all hydrants.)



Instruments we use include:

  • Two 0-200 p.s.i. pressure gauges with garden hose connections

  • Two 2" to garden hose reducing caps

  • One 4" to 2" reducing cap

  • Two pitot gauges;

    • 0-30 p.s.i.

    • 0-100 p.s.i.

  • Adjustable hydrant spanner

Other Equipment Includes:
  • Diffuser basket

  • Hydrant sock

    (Rubber lined canvas sock attached to a flow tube which can be used to direct water away from sensitive areas.)

  • Rope to tie off end of hydrant sock


Most water systems use chlorinated water. Chlorine and chloramine can be troublesome when hydrants being tested discharge into environmentally sensitive drainages and riparian areas.

Our diffuser baskets are outfitted with nylon mesh covers which contain pockets in which we place large "industrial strength" chlorine neutralizing tablets. Enough material from these tablets dissolves during testing to render chlorine residues in test water non-harmful to fragile plants and wildlife. Chloramine testers can be used to check the neutrality of water discharged through the diffusers.

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Data Needed for Flow Tests

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