Solid Answers from a Solid Machine

40% of a community's fire protection rating is based on water supply. Having complete and accurate records on the performance of fire hydrants is one of the things that the inspector from the Insurance Services Office is going to want to review. Good records require good testing techniques plus a way to take the data recorded from tests and convert that to useful information. The Hazen-Williams formula accurately computes the total flows available from hydrants without having to flow multiple outlets, however the formula is pretty complex.

Calculating the observed flow from one outlet is pretty straight forward but working the Hazen-Williams formula can be a bit intimidating. Then there is the additional variant which involves a different formula basis for low pressure hydrants. There are all sorts of pricey programs and calculators that one can purchase. In 1984 we addressed the problem using a simple but extremely durable and low cost portable computer known as the Tandy Model-100. These tough workhorses are still in service and have never seen the shop.

We purchased two Model-100 computers in 1984. They have 8085 processors that may be considered primitive by today's standards, however the 8085 was good enough to be used on the Mars Rover. While the Model-100 is a simple DOS machine, it is unbelievably rugged, is "instant on" and runs a long time on four penlight batteries. A year ago we upgraded to Windows based pentium lap tops. The boot up time was so cumbersome that after one day we went back to the durable Model-100s for field use.

Shown with an external 3½ in. disk drive

Data and calculations are stored in a text file and can be uploaded to agency computers via serial or dial-up connections, or they can be stored on a floppy disk. There are still thousands of these portable PCs in use and they are supported by active user groups who maintain spare parts, repair capabilities and firmware upgrades. With respect to repairs, in the 15 years we have had these machines, they have never been to the shop in spite of getting soaked, being dropped out the cabs of fire engines and other forms of abuse. Reconditioned Model-100s are still available. They can be obtained, complete with a basic "shareware" hydrant calculation program for under $300.00 from the Club-100 User Group. More modern Model-102 and Model-200 computers are available for not too much more. Return to Part Four Return to Flow Testing Fire Hydrants Return to Water Supply Index Back to Information Section

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