Plumbing re-routed through attic

I am a professional plumber and I have been using PEX tubing for 20 years and I am also manufacturer-certified to do so.

The only time I've ever seen this green color in PEX tubing it was algae. The pipe was a cold water supply line that was wrapped with heat tape and pipe insulation, and run above ground underneath my camper. When I removed the pipe it had algae growth along its whole length.

However, the algae will not stick to the pipe. When you kill it, it will just wash away out through your faucets; just make sure you remove your aerators in order not to clog them.

1. Shut off the water supply line to your water heater.
2. Drain some water out of your water heater from the drain valve.
3. Disconnect the supply line from your water heater, so you can pour your bleach in from there.
4. Reconnect your water heater and run hot water out all your faucets until you can smell the bleach.
5. After letting it sit for a sufficient amount of time, flush all the water out of your hot water pipes and water heater until no more bleach is detected.

This will kill your algae, but you may still have it inside your pipes. You might need to tap on the pipe to knock it loose before flushing.

In my case I drained the pipe and the algae dried up and fell from the pipe. Or you could remove and replace the affected area.

You are definitely running a risk of freezing these lines in an unheated space. It is never wise to run water lines in an outside wall or above an insulated ceiling in an unheated space.

Perhaps you can do one of the following:

1. Run the lines under the floor in the basement (not unheated crawl space) where freezing will be much less likely.

2. Run the lines under the insulation in your ceiling next to the heated drywall. If you have to drill holes in ceiling joists, be sure they are at least 2 inches from ceiling to prevent accidental puncturing from drywall screws. Apply the insulation over the lines.

3. Thermostatically controlled heat tape can work, but be absolutely sure it is installed properly and if possible use a heat tape that you can use pipe insulation over. Not all heat tapes allow use of pipe insulation due to overheating of the PEX.

4. If you do have to run in this area, be sure there are no drafts that can come to bear on the tubing. Freezing is always faster if a cold draft blows on a water line.

I wish I had a foolproof method for you to use. Just be cautious, monitor the conditions and have a water shut off handy. Although PEX will handle a lot of freezing without bursting, a leak is going to be a very expensive fix and a mess to clean up. Good Luck