The Fire Pumper vs. Direct Water Pressure
Showing Advantages That Mobile Unit Has Over System of Raising Pressure at Pumping Station to Fight Fires— A Concise Questionnaire Sent Out by Water Company
THE following article prepared by Charles R. Henderson, president Davenport, Iowa Water Company, besides giving some interesting statistics as to pressures in water departments is significant as showing how largely the plan of raising pressure for fires in water scorks is being discontinued. The use of the automobile pumping fire engine taking the place of this dangerous practice. The article also, incidentally ill u strates hose compact and concise a questionnaire of this kind can be made so as to cause the recipient as little trouble as possible in filling it out.
There seems to be no good reason why the dangerous and wasteful practice of increasing pressure o n hundreds o f miles of Water mains, every time there is an alarm of fire, should be continued. It was at one time the best method, especially so in small towns where a pressure adequate for fire streams was not necessary for domestic supply and the domestic pressure was not adequate for fire streams. Mains then were small, hydrants were far apart, fire departments were manned by volunteers, steam fire engines were expensive to install and expensive to keep in readiness for service, requiring additional horses and one or more skilled mechanics to operate the engines.
Conditions have changed. The automobile has revolutionized fire departments as well as many other things. Now the same vehicle that carries the hose, the men and the tools, to the fire, is also the fire engine when a small and inexpensive pump is added to the apparatus. The driver of the automobile apparatus is also the “engineer” and “fireman” of the pumper.
Some cities are already giving up the practice of raising pressure in the mains as the fire departments acquire pumpers. Why?
Mains and Service Pipes Ruptured by Pressure
In one city requiring all service pipes to he of lead, one-half of all the 2-inch lead services in use have ruptured, and the reason given is the stretching of the walls of the pipe due to frequent increase of pressure. Plumbing is without doubt seriously damaged by change of pressure. Elevated storage reservoirs which serve as equalizers to the pumping rate must be shut off from the distribution system when direct pumping beyond the head produced by the height of the reservoir is required. This seems to be very bad practice, requiring strain and a dangerously high rate of pumping during some fire alarms which occur at times of heavy domestic consumption.
In some cities mains, of twelve inches diameter, and over, have burst during time of carrying fire pressure, virtually putting the water department out of business until such mains were shut off. It sometimes happens that in changing the adjustment of the steam valves on a large pumping engine to effect a change of water pressure the pumping engine is accidentally shut down. The writer saw one accident of this kind which resulted in a city of 50,000 population being entirely out of water for nearly half an hour. If there is any time when conditions in the pumping stations should be more free from the danger of accidents than any other time, it is when there is a fire. Increasing pressure for fires is the cause of strain, excitement and, often, accidents that tend to cripple the water department.
Sixty Pounds Pressure Ample for Ordinary Purposes
A pressure of sixty pounds (138 feet) will supply all but very high buildings with a satisfactory supply for domestic purpose without re-pumping at the building; then if the mains are of proper size the fire department can obtain enough water for any fire at good pressure. Such a pressure is ample for automatic sprinklers and is enough for small fires requiring one or two lines of hose.
Ordinarily, firemen do not require more than 40 to 45 lbs. pressure at the base of the nozzle. Large fires require more pressure than any ordinary water works can safely carry because to lay many lines of hose requires some very long lines. Large nozzles require either more than one line of hose to supply them or else high velocities in the hose line and that requires high pressure at the hydrant. Powerful streams require more than 45 lbs. at the nozzle.
Should Provide Pressure Through Pumpers
It should be the duty of the water department to furnish the water in sufficient quantity at ordinary pressures suitable for good domestic service and all higher pressure required should he provided by the fire department using pumpers or fire engines.
It is so easy, and such a temptation, to send out a questionnaire; and then it is getting to be a general habit. Quite often the information requested is very valuable to the operator of a utility or department, so rather than run a good thing into the ground it would be better to give thought to the practice so as to preserve it. Water works superintendents in 143 cities in the U. S. having populations over 50,000 were asked by the Davenport Water Company, of Davenport, Iowa, for information regarding pressure in the mains of their respective cities. The 143 cities included all in the class over 50,000 population. A letter was written explaining exactly what data was desired and a stamped, address printed, postal card was enclosed with the questions and spaces for answers also printed thereon.
Easily Answered Questions Asked
Only questions were asked that could be answered without effort or looking up. The high percentage of replies (over 80 per cent.) encouraged us to follow up those who did not reply with a second letter which brought in all but a few. Those remaining were obtained by sending a card to the chief of fire department or the city engineer until 100 per cent, replies with the information were obtained. Since then many of the duplicate cards sent out have been straggling in so that in several cases we have received duplicate or triplicate replies. Sometimes a slight difference has been noted in the information coming from different sources, as would be expected.
Only One Refused Information
Only one man refused to give the information, and he stated, after the second request, that he would have no time for anything else if he answered all the questions people asked. It is in sympathy, to a slight extent, with his point of view that we suggest that more thought be given to the preparation of a questionnaire and, especially, that the author of a questionnaire put himself in the place of the man who receives it, as a test to learn if it is brief and considerate. Our experience shows that consideration pays in large percentage of replies.
The Letter and Questionnaire
Superintendent Water Works:
Davenport, Iowa, March 18, 1922.
Dear Sir: Will you please give us the information asked for on the enclosed stamped and addressed post card.
We wish to know how many cities having more than 50,000 inhabitants increase the water pressure in domestic water mains when there is an alarm of fire. We also desire to know what normal water pressure is carried in commercial and residential districts of cities in this class.
Your courtesy in mailing the card will be very much appreciated.
Yours very truly,
DAVENPORT WATER COMPANY,
C. R Henderson, Manager.
The name of the city answering was written on the reply card before it was sent out. No signature to the reply was required.
Answer by City of……………………………………
Question : What is the normal water pressure in your prin-
cipal mercantile district?
Answer…………………..lbs. per sq. inch.
Question : What normal pressure is carried in a fairly rep-
resentative residential district?
Answer…………………..lbs. per sq. inch.
Question: Are above pressures increased in time of fire?
If so, how much?…………………………………….
Does your city possess a high pressure system? …………..
NOTK—Pressure understood to he approximate only and refer to street level or at fire hydrant.
Table Result of Questionnaire
The table herewith has been prepared from the answers to inquiries sent out to the 143 cities in the United States having a population of more than 50,000 according to the census of 1920. This table shows that domestic pressures in commercial districts range from 20 pounds per square inch to 145 pounds. Domestic pressures in residential districts range from 25 pounds to 125 pounds. The average reported pressure is, in commercial districts 68 pounds, and in residential districts 56 pounds. Not more than 25 per cent, of the cities raise pressure at time of fire.
The amount of the increase of pressure ranges from 4 pounds to 55 pounds. The average is 24 pounds.
In the larger cities such as New York, Philadelphia and Baltimore, high pressure hydrants supplied by separate high pressure mains are available in high valve districts and that, of course, is good practice and will doubtless extend to other cities in time.
The Illinois section of the American Water Works Association, the Indiana Sanitary and Water Supply Association and the Iowa section of the American Water Works Association have adopted resolutions, which have been published, advocating the discontinuance of raising pressure during fires and it is strange that such a reasonable and apparently necessary reform was not started sooner.
Table of Water Pressure in 143 U. S. Cities
(Continued on page 541)
Fire Pumper vs. Direct Water Pressure
(Continued from page 530)
- Increased on special call above 10 pounds.
- Increased for very large fire.
- In Mercantile District.
- In year 1921 raised pressure twice.
- In case of large fire an extra pump.
- High service In Mercantile District carries 107 pounds.
- Are setting away from raising pressure as being dangerous.
- Turn on more water to maintain 60 pounds.
Increase on special request of fire chief. None in a year.
- In some cases maintain minimum of 40 pounds.
- Formerly raised pressure—now motorized.
- Increased In Mercantile District.
- Can raise pressure l5-20 pounds.
Maintains adequate supply—rarely Increase pressure.