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Wood Pipe as Water Conveyor 



"How long will it last?" is a question asked perhaps more than 

 any other concerning the use of wood pipe for irrigation. That the 

 life of such wood pipe should be at least twenty years if the pipes 

 are fully exposed and supported free from all contact with the soil, 

 if the material is either fir or redwood, and if the pipe has been 

 properly maintained, is the conclusion of a specialist of the United 

 • States Department of Agriculture in a professional paper on ' ' Wood 

 Pipe for Conveying Water for Irrigation" (Bulletin No. 155). Irri- 

 gation engineers and the owners of irrigation works will be par- 

 ticularly interested in this new pamphlet which may be had free of 

 charge by applying to the Department of Agriculture, Washing- 

 ton, D. C. 



Many millions of dollars are already invested in wood pipe lines 

 in the United States and this amount is being increased annually. 

 Protection of these investments demands that existing pipe lines be 

 maintained and operated in accordance with what experience has 

 shown to be the best practice. Future investments should also be 

 safeguarded by designing, maintaining and locating new pipe lines 

 according to the best known practices. 



The length of life of wood pipe is dependent on the life of 

 the wood rather than on the life of the bands, although contrary 

 theories were held thirty years ago. Only in rare instances have 

 the bands failed first. Corrosion of the bands being a chemical 

 action requires the presence of moisture and oxygen. It usually 

 occurs most rapidly where pipes are buried and the backfill is wet, 

 under conditions which, as a rule, are most favorable for- the life 

 of the wood. Corrosion is greatly accelerated by the presence of 

 alkali in the soil. 



The decay of wood pipe is due piimarily to the growth of fungi, 

 though possibly certain forms of bacteria may assist in the final 

 destruction of the wood cells. The growth of fungi to au extent 

 detrimental to the life of the wood requires a favorable combination 

 of moisture, air and heat. The exclusion of any one of these be- 

 yond certain limits inhibits their growth. 



It follows that with pipes buried in the ground the wood will 

 endure longest where the air is most nearly excluded, either by a 

 high internal pressure which completely saturates it or by a deep 

 covering of very fine soil. lu accordance with the foregoing state- 

 ment, experience shows that in contact with the soil wood pipe 

 decays more rapidly under a light head than it does under heavy 

 pressure, and other things being equal, it usually decays more 

 rapidly in a porous open soil, such as sand or gravel, than it does 

 in a fine soil of silt or clay, because the finer soil is more effective 

 in excluding the air. Experience appears to indicate also that wood 

 decays more rapidly in a loamy soil, rich in humus or partially de- 

 cayed organic matter,, than it does in one containing little or none. 

 This is probably due to the fact that the presence of organic matter 

 affords more favorable conditions for the development of fungus 

 gi'owths and bacteria. 



Pipes fully exposed to the atmosphere and free from contact with 

 the soil will, as a rule, be too dry on the exterior to favor the de- 

 velopment of fungous spores, and so long as the outside of a pipe 

 remains dry no appreciable decay will occur, even though the inter- 

 nal pressure is very light. Decay of exposed pipes almost invariably 

 starts at the ends of staves, as a result of leaky joints. Where water 

 leaks out and runs down over the outside of the pipe favorable con- 

 ditions are afforded for the growth of the algae, which usually get 

 a start, then mosses may begin to grow in the soil that collects on 

 such spots, and decay spreads to adjoining staves. Bruising the 

 staves in handling or injuring by too tight cinching of bands renders 

 them more susceptible to infection by the spores of wood-destroying 

 / fungi, thus hastening decay. The life of exposed pipes may be pro- 

 longed by promptly stopping all leaks as they develop and by keep- 

 ing the exterior dry. The decay of buried pipes has also in some 

 instances been arrested by removing the covering and leaving them 

 exposed. 



The asphalt r coating applied to machine-banded pipe, 



— 24 — 



while intended primarily as a protection against corrosion of the 

 bands, doubtless helps also to some extent in preserving the wood. 

 Until recently the practice has been to leave the ends of wooden 

 sleeve couplings untreated. These couplings almost invariably decay 

 long before the main pipe. This may indicate that infection by wood- 

 destroying organisms starts principally where the coating is absent, 

 though less perfect saturation of the wood in the sleeves may be the 

 more largely responsible for the early decay, as it may be noted also 

 that decay occurs at summits of pipe lines where air accumulates 

 much sooner than at depressions. 



The practice of coating continuous stave pipe has not been com- 

 mon, but in a considerable number of cases some treatment has 

 been applied for the purpose of preserving the wood. There is wide 

 difference of opinion as to the value of such treatment,- and the 

 effectiveness for the purpose intended may depend also greatly on 

 what is used and how aiid when it is applied. 



On exposed portions of new pipes the United States Eeclamation 

 SeiTice has used a paint consisting of six pounds of red oxid mixed 

 with one gallon of boiled linseed oil. One gallon of the paint was 

 suflicient for two coats on 125 square feet of pipe. On top of the 

 pipe \\herc exposed to the sun and where water from leaky joints 

 luns dov.-n over it this paint does not last long, much of it being 

 gone in two years. Eepaintiug while the pipe is in use is usually not 

 practicable, because oil paint will not adhere readily to wet mate- 

 rial. The use of paint on exposed pipes under ordinary conditions 

 probably adds very little to their life. 



The new bulletin which consists of thirty-seven pages, contains a 

 number of figures and tables of practical use to irrigation engineers. 

 Continuous stave pipe and machine banded pipe are described in great 

 detail and many specific instances are given to show how long wood 

 pipe may be expected to last under special conditions. 



October Forest Products Exports 



The October statistics of forest products exports show a decline 

 of fifty per cent or more for most items, when compared with 

 figures for the same month in 1913. The decline is not universal, 

 however. Trade with some countries shows au increase. Canada's 

 purchases of hewed and sawed timbers from us wore slightly larger 

 than for October last year, but the lumber trade with Canada fell 

 off more than half. Mexico's import of square timber from the 

 United States increased 600 per cent in the same period. That 

 increase was doubtless due to improvement in domestic affairs in 

 the southern republic. The Central American countries likewise in- 

 creased their lumber purchases in the United States. Decline is 

 to be noted in every South American country. During October last 

 year Argentina imported our lunfoer to the value of $597,307, and 

 for the same month this year the purchases there totaled only 

 .$85,359. The showing is still worse for Brazil. Its imports of 

 lumber from the United States fell from $200,252 to $459. In 

 Germany and Belgium imports completely ceased. France's imports 

 fell off 98 i)er cent, and Holland imported from us only 10,000 feet 

 against 7,542,000 in October last year. Our exports to China in 

 the lumber lino were nothing in October, while last year the October 

 exports there were valued at $89,351. 



Following are the totals of our exports of forest products for 

 October 1913 and 1914: 



Oct. lOi;!. Oct. 1914. 



Ilcwed and sawed timber $ 60.3.292 .$ 255.812 



Lumber 5,268,767 l,S87,.'i.'{2 



Furniture 645,508 236.228 



Agricultural Implements 1,813,522 427.087 



Carriages 42,189 11,401 



Wagons 122,721 530,849 



The item showing wagons trfls the effect of the war on this article. 

 The export of wagons to Europe in October this year was 14,000 

 per cent greater than for the same month last year. 



