I am currently a licensed contractor performing remodeling services for residential and commercial customers in Wisconsin.
Hot and Cold Water Lines Should Never Touch
One of the big discussions among building and trade professionals is the use of applicable knowledge and the International Residential Code (IRC) during inspections. While some issues are very obvious, even to the untrained eye, other issues take a bit of knowledge to catch.
The picture above is of PEX hot and cold water lines that have been run through the framing and are touching each other the entire way. This has passed the rough plumbing inspection and is ready for insulation and drywall. However, this installation can cause some issues down the road and is not a typical supply run installation.
Typical Supply Installation
Generally, each hot and cold water line is run through separate holes spaced between 2-6 inches apart, depending on the amount of space that is available. There are a few reasons for this. One reason is for easy installation. Another reason is so that when the water test is performed, the plumber can easily identify a leak if it occurs, and it is not uncommon to have a small leak in a pipe during the water test.
The last reason that is not as obvious is so that the water lines do not conduct energy from each other and form condensation. Think about the amount of energy transfer that will occur with these pipes. The cold water lines are going to be around 60°F while the hot water lines are going to be over 100°F. This is a temperature differential of 40 degrees that will cause the cold water line to form mass condensation on the exterior coating of the line.
The plumbing pictured above has passed inspection as there is no code that states that this cannot be performed. However, a little extra knowledge would tell you that this is not a good plumbing practice and should be corrected to avoid possible issues in the future.
It is always a good idea to have a licensed plumber perform your plumbing work. Plumbing that is improperly installed can be extremely costly and will actually cost you three times as much as it would to just have a professional do it right the first time.
This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.
© 2011 Energy Guild
Brian on February 20, 2014:
Another problem with this installation -- sanitary tees should never be placed on their back. That is explicitly forbidden in the IRC.
Marty Boo on January 02, 2013:
When I saw the picture I instantly thought ,wow that's not good,Then I read your article it was a great way to explain the problems that installation would cause,great article.
Giselle Maine on September 03, 2011:
Very helpful - I never knew about this, nor about the "why" behind the hot and cold water lines not touching.