Pipes for gravity fed solar heater

[cansel]

I'm having a problem with my gravity fed solar heater. I live in Yucatan and temperatures are extremely hot. I've had several hoses melt when left out in the sun and now my latest heat victim is the CPVC breather pipe attached to my solar heater (pic below).


I'm also noticing that the pipes feeding in and out of the solar heater are getting black. The sun is very hot here... I may try using a metal breathing pipe instead of cpvc and am thinking of mixing in some cold water on the outlet to reduce the temperature of the water feeding the system but does anyone know which pipes would withstand high temperatures? They don't do copper here and I won't even attempt to assemble copper piping DIY. I looked at HDPE but they only withstand 82c (179f), like CPVC. The other solution is to cover the solar heater to avoid it getting too hot but that's just impractical for me. Has anyone else had this problem? Any potential solution suggestions?

Thanks!

 

[SolarRich]

I have those evacuated glass tubes on a ground mount. It is a pumped system unlike your gravity system. Looking at the temps those collectors can run at, I had to use copper piping for everything. The copper pipe was many times more costly than anything plastic. Copper is the only thing I know of that will work at those temps.

 

[400bird]

Can you get any type of metal pipe? As far as I know, none of the plastic pipes are rated for sun exposure.

 

[1234enough]

For a laugh I placed a beyond serviceable solar evacuated tube in the sun for 15mins and then poured water down it, the pops and steam where a good reminder that they can get extremely hot if not enough thermal cooling is taking place.
Always design either enough thermal storage capacity for what the system can produce or a thermal dump load is required, if not then overheating will occur.

 

[whattheheld]

I would use a galvanized pipe for the breather. On pump ends we use brass and then pvc to let the heat dissipate a bit. Might go that route or just buy some of those flexible stainless steel water heater connectors

 

[cansel]

I would use a galvanized pipe for the breather. On pump ends we use brass and then pvc to let the heat dissipate a bit. Might go that route or just buy some of those flexible stainless steel water heater connectors

Thanks. I think the galvanized pipe might be the best solution and then use brass/stainless fittings on the outlet before the mixing valve.

 

[cansel]

I have those evacuated glass tubes on a ground mount. It is a pumped system unlike your gravity system. Looking at the temps those collectors can run at, I had to use copper piping for everything. The copper pipe was many times more costly than anything plastic. Copper is the only thing I know of that will work at those temps.

This is Mexico, and Yucatan at that. I'd have to learn how to solder copper pipes or import a plumber to do it which would be exorbitant for me. Using a mixing valve and temperature gauge on the outlet will be less costly. I may even use a shade screen during the dry season. We're in March and the real heat hasn't arrived yet...

 

[sumpower]

Shade cloth from a greenhouse supply store. We used a 40% shade cloth so are solar water heater didn't overheat. Just had to buy it with grommets pre-installed for points to secure it.

 

[SolarRich]

I had to learn how to solder copper pipes when I put my HW system in. Prior to this most of my soldered copper pipe connections leaked and I had to do them over again. And over again

But i was determined to solder the connections right this time. And I did. Not one leak....

 

[rcrracer]

There is such a thing as aluminum threaded electrical pipe. Its similar to rigid or imc and uses national pipe thread(NPT). It uses regular threading equipment. Another type of tubing/hose that is subjected to hot water under pressure are the supply hoses for washing machines.
They appear to use garden hose threads(GHT). There are adapters on Amazon that convert from one thread type to another.

 

[HarryN]

Soldering copper tubing and fittings together is pretty easy, but it is a lot easier if you are around someone that has done it.

Basically a mapp gas torch, flux and solder paste.

A propane torch was used historically, but now map gas is really required to get hot enough for lead free soldering.

Solder the tubing straight and L pieces together.

Then solder on the tube to pipe fittings as needed.

The key might be a matter of terminology - you are looking for copper "tubing", not "pipe".

You have to be absolutely consistent on the "type" of tubing and fittings that are used, or it does not work / fit together.

Copper tubing - Wikipedia

en.wikipedia.org

https://www.youtube.com/results?search_query=copper+tubing+soldering

Soldering method for pure lead solder, which is not really used anymore in the US, but use lead free if you get into using it for drinking water use.