[Geo NR Gee]

Thank you for opening this post. Short version is I have a lot of evacuated tubes sitting on the side of my house collecting dust. I am getting help today to install the racking for the tubes and maybe the tubes.

For the last few weeks, I have been looking for the proper way to use them in a drainback system with water (no antifreeze). These are the Thermomax HP200 tubes and are about 7' per section. They have snapdiscs in them to prevent overheating. Mine are the 195* cut off ones I believe.

Experimenting with the different drain slopes yesterday was to fill the manifold on one end with water and measure how much came out at a specific angle.

It seems like the acceptable result was 1 tablespoon of water left over in a 7' section at 9:12 pitch or 4.4* angle, slope is 7.7% according to the slope calculator. With 3-7' sections, is that a problem for freezing?

I have done weeks of research and frankly it's just going to sit another year unless I just get it done. Hoping someone can save the day before we make a big mistake.

I watched videos by Dr. Ben and he shows many viable ways, but I only see he recommends 1" in 20' or 1/4* slope, however I think that is for a unobstructed manifold. The Thermomax manifolds and other evacuated tube collectors have the heat riser pipe going directly into the liquid stream of the manifold. I tried that with the Thermomax manifold and it is way to much water left inside of the manifold. The 4.4* angle slope is much better if a tablespoon of water over the entire 7' length is acceptable.

Geo