I set out to insulate the hot water pipes in my basement today and discovered that the plumber had installed these brackets every foot or so, making it difficult and impractical to wrap the pipes. Is this normal?

A run of 4 PEX pipes (two hot, two cold) using a 4-pipe bracket on every joist

In this picture you can see a run of 4 PEX pipes (two hot, two cold) using a 4-pipe bracket on every joist. This is in New England and it takes forever to get hot water at any tap in the winter.

  • 2
    PEX has a tendency to sag if not supported well (install looks nice). Are you talking heat wrap or just insulating them? If just insulating maybe a simple trough with pink insulation in it screwed under them? They also sell a hot water circulator that is install at end of hot water line to keep a bit of a flow in the line keeping it warm. Dec 30, 2016 at 18:45
  • @spicetraders My plan was to take some measurements, get some foam tubes, and cut to fit, but it doesn't look like there's room for it, and there would be so many cuts that the insulation would be compromised. Also since that run is alternating hot and cold I'd want to insulate separately, right?
    – jelder
    Dec 30, 2016 at 19:21
  • As far as insulation it's a game of surface area, and every bit helps. After all, people still insulate their walls even though their windows are worse than an uninsulated wall... Dec 30, 2016 at 19:54
  • 1
    Love the workmanship on the pex. Not in love with the 1 mile long horizontal waste line.
    – DMoore
    Feb 1, 2017 at 17:35

1 Answer 1


Insulation won't make hot water come faster

When you open the valve initially, the hot water pipe is full of cool water, because it cooled off.

Pipe insulation won't stop the cool-off, just slow it down a little, not enough to matter unless you are following someone else into the shower. After even 20 minutes of disuse, the water in the pipe will cool significantly and you'll have to start over. Start what over?

Out, darned pipe!

The pipe is now (at best) a very tall piston full of cool water, and the hot water entering from the heater must plunger the cold water out, via the faucet. The time this takes is determined by VolumeOfPipe / FlowRate. For instance if the pipe holds a gallon of water and flow rate is 4 gallons-per-minute, it'll take 1/4 minute or 15 seconds.

How much volume does a pipe hold? That is Length * 3.1416 * Radius * Radius. The important part is radius is squared, which makes it an extremely potent factor. Double pipe diameter, volume quadruples, and so does delay.

So what happens when a deluxe-minded homeowner decides to increase pipe diameter "to be fancy"? Exactly.


One is to downsize your hot water pipe volume as much as possible. Will 3/8" pipe give a workable flow? You have 2 redundant runs, but that might be better - each one has its own dedicated "plunger" of cool water to purge, but the lines would be able to be smaller, so less delay.

Do you have a ton of extra electrical capacity in the house? The single best way to move hot water across a house is fat AA-8000 electrical cable supplying a tankless heater right next to the point-of-use. In a New England home, this takes careful design because you need a lot of temperature rise.

Do you have enough electrical or gas/venting capacity to add a second tanked heater at that end of the house?

Or given your usage, should the main heater really be there instead?

  • It's all new construction (less than 6 months) so we're not likely to change the pipes. It does have a tankless water heater though.
    – jelder
    Dec 30, 2016 at 20:44
  • Did the delay get singificantly worse when you changed to the tankless? Sometimes certain patterns of draw will cause them to misfire. Dec 30, 2016 at 22:49
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    This is a new house; wait for a year and get to know the water system as it is. This will give you time to notice any leaks at the splices. Insulating the PEX tubing in the basement will not significantly speed up the arrival of hot water. You definitely would not want to put the hot and cold piping in the same insulated envelope. What brand and model of tankless heater do you have? What temperature are you setting it deliver? Dec 31, 2016 at 9:51
  • All this, plus the fact that pex is a reasonably good insulator as it is. You won't change things by adding more.
    – isherwood
    Feb 1, 2017 at 17:48

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