We have the same issue - FL repipe with CPVC. The pipes make noise after hot water is used in the mornings...it clicks, like a dripping sound for 10 minutes after the water has stopped. This is in the summer. We had the plumber come back out and they loosened some of the straps. This provided quite a bit of improvement as the issue is only in the mornings now and not throughout the day as it was before. The issue, I think, is because the pipes travel so far. We have a one story house and the pipes are in the attic. It is the strapping, I believe, that is causing the pipes to make the "dripping" sound. It is VERY annoying to me, but it does not bother my husband (he is the one showering in the mornings while I am sleeping). The sound wakes me up. I would have gone with PEX had I known about the sound issue. The concern I have is the stress on the pipes/straps causing damage on the joints/connectors.

The coefficient of expansion is different for each size of pipe, but for illustration let us consider 3/4" CPVC. For 3/4" CPVC the expansion is 1" per 100' of pipe for every 1degF of temperature change. Assuming the pipe begins at an ambient temp of 70 degress when you start your shower and the hot water is set for the code max of 125 degF the temperature differential in the pipe would be 125-70 = 55degF. The thermal expansion would then be 55" per 100ft of pipe. We rarely see a run of pipe longer than 50' in a residential system, but even at 50ft the thermal expansion would be 27.5". The CPVC installation handbook suggests a 18" expansion loop at every 30' on a straight run and the loop should be located near the center of the run. To make the expansion loop the pipe is cut and a 90deg elbow is installed. The line is then stubbed out 18" and a 90deg elbow is installed. A short 4 to 6" length of tubing to another 90deg elbow turning back towards the original pipe and then connect the loop to the original pipe with another 90deg elbow. On the ends where the pipe drops down through holes the pipe should be run about 18" to one side of the hole with an 18" offset from the pipe to the hole. IN this manner as the pipe expands the 18" horizontal offsets can flex slightly to absorb the expansion. Insulating the pipe will not prevent the expansion because the temperature differential results from the temp of the liquid in the pipe, however if the pipe is first insulated, then pipe hangers large enough to fit the exterior of the pipe insulation are installed, the pipe is free to move slightly within the insulation. If you have your water lines run through the attic space you definitely want the cold water lines insulated, otherwise as the pipe cools from the cold water moisture will condensate on the pipe and drip down on your ceiling causing water damage the same as a leak.

Tools and procedure is actualy quite simple but mistakes or unexpected breaks while working on water supply can change things , ( think water turned off to intire house while searching for a plumber ). This is what I suspect is causing the noise. A loose washer in hot angle stop ( shut off valve where pipe exits wall beneath sink). 90% of the time this is the cause. The single valve can control facuet and dish washer both or there can be 1 valve for each. If each has a valve,turn the one for facuet off. Start washer and when noise starts adjust the valve for washer( slowly turn off and/or on. If adjusting valve stops noise, you can leave it in that position until your brother-in-law can come fix it or turn hot water off at heater or main supply to house. Open the offending valve about mid way then unscrew the cap between valve and it's knob/handle. When the threads come free of valve turn valve to full open and the stem handle assembly will fall free. The screw holding washer will not be tight if my hunch is correct. You can install a new washer or just tighten the screw. Lub stem and cap with silicon grease,WD40 or the like. On reassembly,screw stem in about half way then thread cap on and snug it a little more than finger tight. Turn valve off and restore water supply. Have wrench ready to tighten cap and turn valve on. The valve will likly leak between cap and stem. Slowly tighten cap until leak/drip stops. You can't buy parts for the valve so don't overtighten and bust the cap. If the leak doesn't stop without overtightening,remove the stem again and take it to the local hardware so the clerk can help you with correct packing. If adjusting the angle stop fails to quite the noise don't take it apart,post back and we will look elsewhere.

Thanks for that link - very helpful read. So, I'm still trying to wrap my brain around all this before I go to far. Let me explain. First, I'm trying just to understand how this works. I understand it in theory and in that article but, in our setup, it looks like all it is really servicing is the water spigot on the side of the house. The water comes in from the left, down into the tank and also to the right through the honey well then just... on to the water spigot that comes off the house. That's it. Now, I CAN simply unthread the pipe a bit further down, and then into another pipe right by it, to hook the house to the well water in an emergency - as it was shown and explained to me by the seller. So, is it to keep and regulate pressure to the house, its there just in case of that? That might all make sense to me except, why does it make the bang sound when I use water out in the yard from a different spigot. I can't seem to understand how it is even involved there. I see the one pipe go into it. That's it. So anyway, on to what the article says, and others after I've googled a bunch. So, banging on the side of it, it does sorta sound more thud ish than hollow, so I do wonder if it is water logged. I understand if it is water logged the pump will turn on immediately any time you use the water. That is the case here. It does have the air valve at the top, and air does come out - not water. So that is good. I read I need it to be pre charged to the psi (minus 2) of what the pressure needs to be for the pump to turn on. Or two less than the .. in (something). I can't find the exact term again as I type this but it was in-something. SO now what I'm trying to figure out. How do I find out what that number is, I don't see anything on the pump. Am I to put the pressure valve on the drain at the bottom and see what it is? If it's over pressured or under pressured wouldn't that give a bad reading? Is that what the honeywell is for? It says 50psi It looks like on the right. I don't know what the "diff" is on the left. So, should I turn off the pump, drain everything, drain the tank, then pressurize (or depressurize) the air to 48 psi? Everything I see says this is a simple task and I feel like I'm almost there, almost understanding it... just not quite there yet. One thing I do know for sure, it's a good sign water didn't come out of the air inlet. ;)