Flow, Swing, & Spring Check Valves

I somewhat understand what their intended uses are. But when & where are they to be installed?

Am I correct in that flow (weighted) & swing check valves are only to be installed in a horizontal position and a spring check valve can be installed in any orinetation?

I'm trying to decide what valve(s) to install in the supply manifolds of two boilers plumbed parrallel to prevent water circulation from one to the other. I know swings are out but why not a spring? They're 1/3 the cost of flow checks.....

I don't know if a spring check would work or not. I used a taco weighted flo - check on my system. It worked as designed and kept the wood boiler piping cold when the oil was running.

I actually just took it out because I'm adding storage and using a zone valve instead. Its 1.5" and Id sell it for 25 plus shipping if you can use it. It was in use for a year.

http://www.pexsupply.com/Taco-222-6-1-1-2-Universal-CI-Taco-Flo-Chek-1993000-p

Correct a weighted check needs to be installed so the weight can work

The advantage to a spring check is can be installed any position. They usually have a better sealinbg surface for tight close off. Also the spring checks designed for hydronics have a cone shaped design and a soft seat so they don't clatter, if that's a word. The cone shaped disc offer a smoother flow pattern then a flat disc check used for sump pumps.

Neoperl makes the checks that are found in most circ pumps these days, and many other hydronic components, they have a 1/2 psi 'pop" to them and work well with small, low flow circs.

Check the Cv, if you oversize a check the valve can flutter if you do not have enough GPM to hold it fully open. Often times a check one or two sized smaller then the pipe is sufficient. Check the temperature rating also.

I used simple swing checks in mine to do that. No issues so far.

Sounds like flow checks are the preferred at each boiler manifold. Besides, I'm having difficulty locating a swing check with a greater than 180 degF rating.

On another note, I have a 1-1/4" spring check sitting on the bench. Looking to use this in lieu of the P.A.B. in my diagram. Any thoughts?