36 BULLETIN 155, U. S. DEPARTMENT OF AGRICULTURE. 



At one point some distance below the intake where uncovered for 

 repairs, the stares of the lower half of the pipe were found to be de- 

 cayed to a mere shell. The 4-inch spacing of bands indicated a fairly 

 good internal pressure. The backfill was stony. Near the dam, 

 where the pressure was not more than 10 or 15 feet, the staves were 

 badly decayed, and it is probable that much of the pipe was in poor 

 condition at this time. On a bridge where it had always been fully 

 exposed there was no appreciable decay of the staves other than at 

 leaky joints, and the same was true along the top of the pipe where 

 exposed or covered with only an inch or two of coarse soil, which 

 permitted it to remain dry. 



E. M. Hosea, chief engineer of the Colorado Fuel &• Iron Co., 

 writes as follows about a pipe several miles long : 



The oldest line we hare — 28 inches in diameter — was built in 1900. For 

 five years past it has been repaired in places by inserting new staves where 

 old ones were badly rotted on the exterior. This allows bands to sink into 

 soft wood and staves to leak. The rot progresses until one-half to three-fourths 

 of the wood is rotted. It occurs in patches, or on certain staves their full 

 length, according to amount of pitch in the wood, or some variation in its quality. 

 This pipe was of Texas pine staves. I should add also that the bands become 

 rapidly corroded where leaks have formed and ground is moist, and I should 

 doubt a life of 20 years for this line even if repairs are kept as above indicated, 

 where we are constantly putting in new fir staves and some new bands. 



This pipe is laid in fine adobe soil and covered to a depth of 2 feet 

 or more. 



By the side of the pipe just mentioned, and under the same condi- 

 tions, a 48-inch fir pipe was laid in November and December, 1906. 

 Mr. Hosea says that in three years it was decayed sufficiently to cause 

 leaks. "When inspected in October, 1913, it showed serious decay, 

 and was being incased with reinforced concrete. This pipe was 

 covered with the adobe soil from 18 inches to 2 feet deep, and where 

 examined was under a head of perhaps 30 feet or more. In most 

 instances the decay extended half way through the staves. Some- 

 times a sound stave occurred, while those on each side of it might be 

 badly rotted. The bands were in good condition and only slightly 

 corroded. Twenty-five other pipe lines built by this company about 

 the same time as this one have also been incased with concrete, decay 

 in the case of each having made more or less progress. 



Under date of May 15, 1912, L. B. Youngs, water superintendent 

 of Seattle, Wash., writes as follows: 



The first wood pipe that we installed in this city was put in 12 years ago, 

 and was made out of our native timber here, known as Douglas fir. * * * 

 In clay soils the pipe lasts fairly well, and I would place its life at from 12 

 to 20 years ; in sandy and gravelly soils I would place its life at from 7 to 12 

 years. However, in the case of large pipe with individual bands the cost of 

 reinstallation would be the cost of the wooden part of the pipe only, as we 

 find the iron bands to be in good condition after 10 to 12 years' service, so that 

 they could be used for the new wood. 



