A Double Check Valve Assembly shall be installed at each noted location to prevent the unwanted reversal of polluted water into the potable water supply.

双止回阀总成应该安装在每个值得注意的位置，用于防止污水出现不需要的回流而流进饮用水供应系统中。

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Still, a bullish double-bottom reversal pattern may be forming on the daily bar chart.

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Bulls have gained upside technical momentum recently and a bullish double-bottom reversal pattern has formed on the daily bar chart.

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However, good gains in the near term would begin to produce a bullish double-bottom reversal pattern on the daily bar chart.

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