My Two Flow Deflectors

The larger unit at the top is built from a brass fire hose female end and has a fixed 2 ½” opening. The total length is about 18” and is made from all scrap parts, which took about 1 ½ hours time, some 25 years ago.

The lower unit is 2” threaded conduit coupling. One part is ¼” X 1” X 3 ½”, two parts are ⅛”X 2” X 10”, one part is ⅛”X 1 ½” x 4 ¼”, and one piece is ⅛”X ¾” X 2”, all welded steel construction. One brass adaptor is 2½”  female fire thread to a 2” male pipe thread. These adaptors can be bought with  2”   or 1⅞”   openings, depending on the manufacturer,  accurate within 1/16”  (that’s close enough), this one is   1⅞”.   One 2” to 1 ½” threaded reducer and one each fitting with smooth rounded edge openings  of 1 ½”– 1 ¼”- 1” and ¾” all parts were bought from a local building supplier for less than $50.00  and will produce readings and flows plenty accurate for any practical use.

Pressure Gauges & Cap Gauge

We did some comparison pressure tests on three gauges, these two were very close at 25 P.S.I. The compound gauge used on this pitot tube is about 2 P.S.I low. This arrangement of threaded cap with cross allows air relief, static pressure reading and flow pressure readings up to 30 P.S.I, all with just one unit.

Hydrant flow

With the hydrant flowing through the 1⅞” opening both cap gauges show 22 P.S.I residual, the pitot tube shows about 20 P.S.I. Two pounds lower, same as comparison test showed. The gauge on the pitot has seen a lot of use, the others are both new. This clearly shows a cap gauge residual reading or pitot flow pressure reading are essentially the same.

Static, 42 P.S.I.               Flow, √22= 4.69      1⅞  X 1⅞   =  3.5156

4.69 X 3.5156 X 29.8 X .9 = 442, rounded to 445.                 A RED  hydrant less than 500 G.P.M.

Static 40 – 41, using 2 ½” flow deflector. Cap gauge 14 P.S.I.  Pitot gauge 12.5, just under 2 P.S.I difference.

2.5 X 2.5 = 6.25                 √14= 3.7416 X 6.25 X 29.8 X .9 = 627, rounded to 630.

Hydrant color ORANGE, 500 to 1,000 G.P.M.

Flow pressure deflection through the 2 ½” & through the 1

Using both deflectors, one 2 ½” and one 1⅞”. Flow pressure 25 P.S.I = 840 + 470 = 1310. A GREEN hydrant 1,000 to 1,500 G.P.M. Deflectors break up the streams NO DAMAGE to road surface, shoulders or ditch banks. Bright yellow barrel with color coded caps and bonnets. Hydrants with a flow of. 1,500 G.P.M or more would be BLUE. This is the NFPA Standard and works quite well for these systems that actually have some strong hydrants. However, there are still small towns and rural areas protected by fire departments whose largest pump is a 1,000 G.P M unit. In these cases the value of a 1,500 G.P.M plus hydrant is questionable but the value of knowing the difference between a 600 and a 900 is not.

Up to 1998 the fire district serving my home town of Rosebud, Missouri  and our neighbor Gerald, Missouri did not have a pumper larger than a 1,000 G.P.M and both towns used a shrunken color code. Hydrants flowing less than 500 G.P.M were still RED, from 500 to 745 were ORANGE, from 750 to 995 were GREEN, and 1,000 G.P.M or more were BLUE. That worked just fine for us for several years. When the fire district got a 1250 pumper we went full scale, a very simple change. All REDS stayed RED, ORANGE stayed ORANGE, GREEN became ORANGE, and most BLUES became GREEN. We do have a few that stayed BLUE at 1,500 G.P.M or more.

While this may not be for you, it did work for us. It helped encourage line flushing and flow testing, good hydrant maintenance, also painting and record keeping by both the City Water Department and the Fire Department personnel.

It helped personnel take more interest in and to better understand flow hydraulics and the value of circulated small piping.

Think about it. It’s not so important for everyone else to know, but it’s VERY important for YOU to KNOW YOUR SYSTEM.