View Full Version : Insulation on CPVC / Recirculator
06-16-2010, 01:39 PM
So my place is run with CPVC. Its in the crawl space in SE US and there is absolutely no insulation on any of the pipe. We have also noticed that it takes 5 or more minutes for the hot water to become hot when running the shower, etc.
I'm having my crawl space sealed along with my new A/C unit so the space will be semi conditioned vs the pretty much open to the ouside shape its in now.
So I was considering adding some insulation to the pipes and possibly adding a hot water circulator. Any advice on type of circulator or on type of insulation to use on the pipes?
My house is farily long compared to its width and the new water heater is going to be way at one end of the house (in the garage).
My new A/C is geothermal and will have a desuper heater on it. I'm contemplating using a tankless electirc (I have the current available and no gas near me), but may end up going with a hybrid heat pump model since it'll be in the garage and its 90+ all summer long here and will probably be way more efficient than the tankless.
What I was thinking about doing after they remove all my ducting for the new A/C and since I have to do a bunch of this anyway to relocate the water heater is add a loop in the crawl space that can circulate water such that there will only be the run to the second floor which is only like 10' of 1/2" CPVC so that would cut the distance the water runs by a ton. I can easily insulate all that pipe since its exposed in the crawl space.
Then see how that goes. If its not enough, I can add a valve to circulate water from hot to cold at the fixture to try to warm up that run.
06-16-2010, 01:54 PM
You especially want to insulate the lines if you are going to add a circulator! A dedicated return line should bypass the complaint of the cold water being too hot. In my case, it returns to cool if I just flush the toilet, but some aquastats get it warmer, so the cold would be, too.
Depending on how far apart from the main line and the point(s) where you end up looping back, would suggest the type of control you need for the recirculator. On some, you put a valve at each location that opens when the water gets cool. On others, it just runs all the time. On the one I have, the pump only runs when it senses it needs to based on the aquastat. Some will accept multiple inputs. Some can be hooked to only enable them via various controls, such as motion sensors, momentary contact switches, or simple timers. the pumps are generally quite small, and except for the heat lost through radiation, the cost for electricity is nominal. If you do a search, you'll see various brand recommendations. the one I have is from RedyTemp. Most of them put a pump by the tank, this one (at least with the model I have) has the pump under the furthest vanity, which requires adding an electrical outlet. In my case, it was easy during remodeling, but might call for another permit and tradesman, if you can't do it yourself, which would add to the cost. If you don't have power in either location, I guess it's a tossup.
06-16-2010, 03:30 PM
Yeah.. i'm trying to avoid the dumping warm/hot water into the cold if I can.
We do plan to do remodels of all three bathrooms, and I do have access to the wall cavity that feeds both upstairs bathrooms (they have a common wall), so I could extend the loop up to the second floor to handle those if the crawl space only loop is not enough.
I dont have access to the wall cavity that feeds the upstairs laundry, but this one doesnt seem to have near the problem of the others as it usually gets hot pretty quick. So I'm hoping this applies to the run up to the 2nd floor bathrooms as well.
So worst case, I'd have to extend my loop to the second floor in the common wall such that theres only a few feet of pipe from the loop to the fixture. Best case, the 10-15' of pipe it takes to get to the second floor and over to the fixture is drained of "cold" water quickly.
So heres a diagram of the proposed loop (give or take 5' on the measurements as I just eyeballed them). The current water heater is located on the 1st floor in a closet about where the loop turns back toward the water heater about 5' away from where the 2nd floor laundry goes up.
I could possibly extend the loop to encompass the 10' run to the kitchen (sink and dishwasher) and the 15-20' run to the 1st floor laundry (not in use as we use the second floor).
06-16-2010, 03:59 PM
Make sure that there is a checkvalve in the system, either built into the pump, or an add-on one.
06-16-2010, 04:21 PM
Is there any type of insulation better for this than others? The foam split tubes always seemed like there could be something better to me.
06-16-2010, 05:53 PM
You need to go to a good plumbing/heating supply store to get some good stuff, or if you can buy from your local Graingers. The big box stores don't generally sell the good stuff. The good stuff has a decent self-stick tape to hold the seam together.
06-16-2010, 08:10 PM
Yeah... the local big box has the self stick stuff, but its about 1/16th of an inch thick.
What you have drawn is about the best you can do without introducing other problems. If the flow went in the opposite direction, then I would connect the circulation line at the sink and go to the heater from there. In your situation, there is no point better than the end of the line, where you show it, to make the connection. At one time, ( I have not seen it lately but then I haven't been looking for it either), they did NOT recommend using a circulation line with CPVC, and were advising anyone with one, to disconnect it.
06-18-2010, 10:10 AM
Any reason they gave not to use it with CPVC? CPVC not able to handle sustained temperature like this? Tried to google for it but not much came up in temrs of saying not to do it.
The problem at that time WAS that the CPVC could not handle a constant high temperature. You might contact the manufacturer of your CPVC and see what the current opinion is.
06-19-2010, 10:27 AM
I do a little more research here and see if theres a CPVC that can handle it.
Would PEX handle the heat better? I could do copper too, but this is all in a pretty shallow crawl space, that would make soldering a bit of a pain. House was built in the late 80s, so guessing it has the CPVC that is here is likely the stuff they warned against.
If we go with a different material for the loop, how far away from the CPVC should I stay? Few feet of uninsulated PEX between the insulated loop and the CPVC enough to buffer the heat transfer. I cant replace all the CPVC (at least not yet) as a lot of it goes up through the walls to areas I cant replace until I renovate those bathrooms, etc.
It is like asking a NASCAR driver how many feet he is supposed to stay away from the car in front of him. His answer would be INCHES, not feet, and that is the same for your question. The two can be inches apart even if there is NO insulation.
06-19-2010, 12:20 PM
Yeah... sort of hard to even ask questions on this cause I cant find much about it one way or the other. Not even the local plumbers have heard of this. Given, I wouldnt necessarily vouch for any plumbers in the area as its expanded fast and there are a lot of plumbers and other contractors in the area that I'm not sure are capable of answering these more advanced questions.
It makes sense to me from a pure engineering aspect. But since I cant find much describing the problem much less any solutions for it, its hard to tell how to solve both my need for a recirculation loop and what materials to use. So PEX is supposed to handle the temperature better since it is used in radiant heat a lot. So the question is how much heat transfer will occur through the circulating water in the insulated PEX loop that'll be 120-150 degress for sutained periods and the water in the CPVC. How much uninsulated pex is needed between the insulated loop and the CPVC that goes to the fixture to allow the heat transfer to be withing operating tolerances of CPVC. If its Inches, would a simple sharkbite tee be enough to cut into the loop and adapt to the uninsulated CPVC. Or do I need a few more inches of uninsulated pex between the insulated pex loop and the CPVC?
I guess I can work through the thermodymics of the heat gain from the water contact vs the heat loss through the uninsulated CPVC, but I'd prefer some more real world examples from a situation that is more specific to this. Anyone actually have a recirculator loop in your house? What material was used for it, etc?