What type of black flexible pipe is used underground to run cold water lines over long distances? Copper Polyethylene PVC Steel

## Step 1<br />The problem is asking us to identify the type of black flexible pipe that is commonly used underground to run cold water lines over long distances. The options provided are Copper, Polyethylene, PVC, and Steel.<br /><br />## Step 2<br />Copper is a good conductor of electricity and is not flexible. It is also expensive and can be corroded by water over time.<br /><br />## Step 3<br />Polyethylene is a type of plastic that is flexible, durable, and resistant to corrosion. It is also cost-effective and can withstand high pressure.<br /><br />## Step 4<br />PVC (Polyvinyl Chloride) is a type of plastic that is not flexible and can be brittle. It is also not suitable for high-pressure applications.<br /><br />## Step 5<br />Steel is a strong and durable material, but it is not flexible and can be expensive.<br /><br />## Step 6<br />Considering the properties of each material, Polyethylene is the most suitable choice for running cold water lines over long distances underground. It is flexible, durable, resistant to corrosion, cost-effective, and can withstand high pressure.