Waterflow Test

[robfipro]

Can someone help me? When performing a flow test today, I opened both 2-1/2" outlets on the hydrant to stabilize the flow and get a better reading on the pitot gauge. Do I have to double the gpm when I calculate my results? Thanks!!

 

[spkreng]

close one of the outlets to get a correct pitot gage reading, I am not sure of the formula but just like getting a reading from the 4 1/2" outlet you have to adjust the pitot gage psi reading bt a coefficient multiplyer to get a correct gpm, not just double it or add together.

spkreng, CET

 

[LCREP]

Yes take a pitot reading on one of the 2.5" butt and the other 2.5" butt, correct for"c" factor for the hydrants butt, and add flows together, done!

 

[cdafd]

Do not see anything in NFPA 291 that says do not flow two 2 1/2 on same hydrant and kind of says you may need to to get a good flow test.

Not an engineer, and have seen both 2 1/2 opened on a flow test. Seems like would almost be the same as when a test header is used, have not seen or heard change in calculations when flowing multiple test header openings.

 

[SprinklerDesigner2]

Every time I have tried flowing both 2 1/2" outlets the needle jumps around so much (it's an oil filled gauge) it is next to impossible to get an accurate reading.

In a situation like this what I have done is use two UL playpipes with tips removed, take each reading separate and add the results. Using two playpipes you will get more water than from a single hose outlet and the pitot reading will be much more accurate.

 

[LCREP]

Hose monsters work well too. And you do not have to get wet!

 

[SprinklerDesigner2]

LCREP,

Hose monsters... I just don't trust them.

I have no reason not to trust them but I just don't. I just got to do it out of the book the old fashioned way getting wet with a pitot.

I would like to see something with 10' of hose I could hook up to a hydrant, maybe two monsters on a single hydrant to obtain a higher flow, but I would be worried sick about accuracy.

Am I concerned about something I need not be concerned about?

 

[LCREP]

Yes!

We, an insurance company have been using hose monsters for many years to conduct hydrant and fire pump tests. Up until we got out of the fire pump testing a few years ago we had 4 units in 50 plus offices in the US. I personally would conduct 50-75 fire pump tests a year using hose monsters. Before that we used play pipes tied to a wood pallet, hose monsters are much better. Most of the sprinkler contractors I see are using hose monsters for fire pump and standpipe flow tests. The pitot less hose monsters are real nice as well as the hose monster mini, lite weight and very accurate.

In one of our training sessions we do at our school we conduct water flow testing off a hydrant. We flow 1500 GPM at a residual of 110 psi!! We use a hand held pitot, hose monster, play pipes, hydrant attached pitots, etc and we find the hose monster is the way to go. We have a remote reader so you are 25' away from the water nice and dry and safe. The hose monster is FM Approved so you know it is going to be accurate. Keep the gauges calibrated, use the supplied hose chart, and you are good to go.

So how accurate is a hand held pitot? How many people hold it in the center of the stream of the water half the distance of the opening away to get a accurate reading as required if you read NFPA 291? When was the last time you looked at the opening on your pitot to see if it was the same size as the day it was new? All it takes is one rock hitting the pitot and so much for your fine tuned pitot. That is what is nice about the pitotless hose monster nothing to get hit by rocks.

Just to be clear I do not sell the product, I have just been using them for the last 15-20 years !

 

[SprinklerDesigner2]

LCREP,

Thanks, I think I will pick up two of them because there are lots of times I would prefer to run both outlets simultaneously on systems requiring a lot of water. A hose monster with just 10' of hose would work well and be easy to work with.

Old dogs, new tricks... some of us just don't like change.

 

[LCREP]

The nice thing about hose monsters is you can do a hydrant flow test on a hydrant on a busy street and not have to worry about stoping traffic. If you add a gate valve to your set up you do not have to worry about a broken hydrant stem when you are flowing 1500 GPM and the hydrant will not close. Close the gate, remove your hose, deal with fixing the hydrant when you can. We use a 10' length of fire hose and it works well. The only other thing you may need is a universal hydrant butt if you run into hydrants that have different threads. Spend the extra $$ and get the 2" pitotless nozzle they are nice, the reduced flow is a concern but you do not have to worry about rocks hitting the pitot. The replacement pitots are about $150 if you go with the 2.5" version. On the 2.5" version the pitot turns, you can flush the hydrant with the pitot away from the stream of water, turn the pitot, and take your reading. They still get hit but not as frequent.

 

[LCREP]

SprinklerDesigner2 where are you located, if you are close to NJ I can lend you a hose monster to see if you like them.

 

[SprinklerDesigner2]

LCREP,

I appreciate the offer but I'm a thousand miles away.

I am going to get purchase a couple of them, even if the do look a bit pricey, because they're cheap compared to an erroneous flow test result. If anything can keep me awake at night it's that.

I sent out all six test gauges I use for annual calibration and certificates yesterday. Two of them I have had for over 20 years and they just keep coming back perfect year after year.

 

[chicopee]

Read my responses to thread 404-354502