What type of pipe insulation to use?

I just put in a hot water recirculation system with a return line to the water heater where the pump is located. It works great! I want to insulate both the hot supply and return lines in the recirculation loop (about 210 feet). I have seen several types of insulation ,i.e.,rigid foam and the flexible rubber type which is much more expensive. I plan to use the one that has the removable tape seal. What wall thickness is suitable? Home depot and Lowes seem to have the 1/2" wall, but my plumber says to use the thickest wall (1"). The 1" is more costly and I have to go to the plumbing supply house to get it. Also is the R value of the rubber that much better than the foam type? And would the difference in cost make it cost-effective?

Armaflex


The same identical product that covers the line sets off your AC unit to outside.

More expensive but worth it.

100% coverage is your goal.

I don't know what is available wherever you are.

Where I am, the removable tape seal costs a huge amount compared to approx 75 cents for a 6 foot tube of soft 'n squishy pipe insulation.

As long as you have 100% coverage - i.e. all pipe is covered with some form of insulation -- then you have done most of the necessary work. Using the most expensive material is an option that makes sense in areas where you want to reduce heat-cold transfer the most. I guess that is mostly near exterior walls.

When you double the wall thickness, you half the heat transfer. Using Zeno's Paradox (halfing the last distance each time) you can see that you a gaining less and less each time you double the thickness. The important thing is that some insulation is applied to every piece of surface, and that there are no uncovered surfaces. The difference between an UNinsulated surface, and a surface covered with ANY layer of anything designed to be a heat-transfer-slowdown layer, is astronomical.

When you double the layer, you gain half of the previous savings. If you don't cover 100% of the pipe surface, your cost savings gain is far far less than what it would be if you merely covered the rest with "something-anything" that is an insulative layer.

david