609.11 Pipe Insulation. Insulation of domestic hot water piping shall be in accordance with Section 609.11.1 and Section 609.11.2.
The water in uninsulated 1/2-inch nominal pipe surrounded by room temperature air cools down from 120°F to 105°F in about 10 minutes; in 3/4-inch nominal pipe it cools down in about 15 minutes. R-3 pipe insulation roughly doubles the cool down time to 20 minutes for 1/2-inch piping and roughly triples it to 45 minutes for 3/4-inch piping. When the time between hot water events exceeds one hour, the water in the insulated pipes is likely to cool down back to ambient, minimizing the benefit of pipe insulation for spread out draws. Based on the Lawrence Berkeley National Laboratory research findings (2012), about 30 percent of hot water draws are within 10 and 60 minutes apart. Pipe insulation will eliminate most of the water and energy wasted while waiting for these hot water draws. See Figure 609.11.
求教各位大地主，房子在加州，两个多月前，第一次slab leak发生在厨房的地底下，property manager 帮忙找了licensed plumber，修好以后，又一个月，又一个slab leak发生在洗手间的地底下。全班修好以后，房客发来照片后，才发现第一次修理的时候，plumber从外面走的热水管，毫无保护，暴露在外面。
第二次修的热水管在车库里，也暴露在drywall 外面。于是责令plumber 去insulate这些水管。plumber照做了，可是越看越不对劲，从来没见过水管暴露在drywall外面的，现在想请教一下各位，这样走水管是符合加州的codes吗？谢谢大家的时间了！
图一是没有insulation的热水管，在外墙。
图二，三 是plumber 加了insulation 以后的热水管，还是在drywall 外面。
房子已经25年了，最近收到保险公司的信件，要update water pipes 的conditions,如果要inspection的话，担心暴露在屋外的管道会有问题。
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609.11 Pipe Insulation.
Insulation of domestic hot water piping shall be in accordance with Section 609.11.1 and Section 609.11.2.
The water in uninsulated 1/2-inch nominal pipe surrounded by room temperature air cools down from 120°F to 105°F in about 10 minutes; in 3/4-inch nominal pipe it cools down in about 15 minutes. R-3 pipe insulation roughly doubles the cool down time to 20 minutes for 1/2-inch piping and roughly triples it to 45 minutes for 3/4-inch piping. When the time between hot water events exceeds one hour, the water in the insulated pipes is likely to cool down back to ambient, minimizing the benefit of pipe insulation for spread out draws. Based on the Lawrence Berkeley National Laboratory research findings (2012), about 30 percent of hot water draws are within 10 and 60 minutes apart. Pipe insulation will eliminate most of the water and energy wasted while waiting for these hot water draws. See Figure 609.11.
便宜很多的心里费，想省点钱完全可以理解。