Flow going the wrong way.

JackW

There doesn't appear to be any sort of check valve between the two tee's at the arrow in the picture below. Since the output (hot) turns right at the tee what is to prevent the return (cold) from mixing with the hot at that point. Shouldn't those two points be separated by using 90 degree elbows instead of being hooked together with a tee above the return pump? Any and all comments greatly appreciated.
Jack

Canucker

No. You want the flows to mix. The required flow rates are different for the 2 zone pumps on the left compared to the needed flow for the boiler that your arrow is pointing to. The difference in pressure that the pumps supply causes the water to flow in its proper direction. If you get an infrared camera on those pipes when it's operating, you'll see the flows and how much they interact

hot_rod

that is primary secondary piping. The boiler circulator should be pumping downward into the boiler, boiler supply to the right.

the dual tees allows the multiple circulators to be disconnected hydraulically speaking. it's possible to have two directional flow between those tees, depending on gpm flow rates of the various circs.

Nice piping, possibly the two zone circulators connected and pumping down from the header, as you have two high spots that could air lock.

JackW

Thank you Canucker. I'm in the process of redoing my 2 zone system and this is the design I'm going to follow.

JackW

Thank you Hot_Rod. Question for you concerning those two high points above zone pumps. Why are they there? Couldn't you just come straight across from the line with the air separator instead of going down, then all the way back up, then down to the pumps?