Do the Taco Mixing valves have to be installed straight up and down, or can they be installed on there side or upsidedown. i know the pumps have to be a certian way depending on PSI. Just didn't know if the valves applied too. Instructions didn't say.

I have a hydro air system in a vacation home and the water stopped circulating. Both circulators feel like they are running but the pipes coming in and out of them are cold. The boiler fires and the supply pipe coming out of the boiler is warm and the temp of the pipe drops off on the way to the spirovent. It seems to me that warm water may not be getting past the spirovent. I tried rapping on it with a wrench but no avail. Several weeks ago, I had a problem whereby I am 99% sure that one of the circulators was not passing warm water. But I am pretty sure that the pipe above the other one was hot. Rapping on the circulator not passing water seemed to get it going. It's lasted several weeks and now neither one is circulating. I am not sure if I have junk floating around in the system and whether it's possible to clog the spirovent from passing water. Along with the initial problem several weeks ago, I noticed that there must have been antifreeze spitting out of the top of the spirovent at times because there was white residue down the side of it, down on the expansion tank below and on the floor. If we think the spirovent is blocked, is there a way to take it apart without draining the system? Thanx