In article . com, randyn wrote:
A few months ago, I had a slab leak in the cold water supply to my
kitchen sink. The plumber rerouted the line through the attic using
PEX, insulated with a black foam sleeve/wrapper.

Now that summer is near, I am finding that, in the afternoon (if the
sun is out and the outdoor temperature is in the 80s or above), the
cold water from my kitchen sink tap is warm-to-hot for 30 seconds or
more before it cools down. The kitchen tap is on the other side of the
house from the cold water manifold, so it is a long run of pipe. I
measured the temperature at the tap with a kitchen thermometer today--
it was 130 deg F for 10 seconds or so, which seems really out of line.
I haven't seen this problem mentioned in other postings to this group
concerning attic routing of water supply lines.

Is this normal for attic-routed cold water supply lines in a hot
climate? I have a hard time believing that the water could pick up so
much heat.

Water is an excellent conductor of heat. Attics can easily reach 130 degrees
or higher. Water sitting in a pipe in a 130-degree attic will become
130-degree water fairly quickly.

My attic has passive ventilation, with no soffit vents.
Would improving attic ventilation result in a big improvement?

Undoubtedly. The cooler you keep the attic, the cooler the water will be.

Or is the plumbing work defective somehow?

No reason at all to suppose that it is.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.