One is 12" tall x 8" wide, the other is 9" tall x 8" wide. Both are sealed plastic units with water flow.Some times we get water hammer from air getting inside at the pump,and we also may at times get extra water pressure. We have to install these valves ontop of each unit at the point of water entry. I was thinking about trying to build a square valve with round male on top and bottom of square box.
Safety relief valve should have the spindle vertical for two reasons:
First, they are set that way and the weight of the spring, spindle,  spring buttons, and disc are all part of the set pressure loading.  Flop it over on its side and the valve will pop early, particularly if it is set for a low pressure or if it has a small orifice. 
Second, The guiding of a safety-relief valve is a little casual compared to, say, a globe control valve.  Flop the valve over on its side and the parts will probably not line up properly because of gravitational side-loading.  Then it will leak.

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