keg washing. why 2 valves on the coupler?

[Pdaigle]

is there is reason why they add 2 shut off valves on the coupler? I know with one is to not lose your C02 but why the other one. is it necessary?

https://www.chicompany.net/images/07D03100.JPG

 

[mredge73]

I don't have any valves on my coupler, just on my manifold.
My manifold has 4 valves: liquid line of coupler (out), gas (in), hot water (in), pump (in).
The coupler valves are probably more useful for purging/filling the keg than cleaning it.

 

[Pdaigle]

how about when filling with C02? you need a valve right since it will come out

 

[mredge73]

You don't want to purge inverted in the cleaning position; C02 is heavier than O2.

It may be useful on the gas line for keg purging but you don't need to hold pressure to purge, CO2 will sink and everything else will find its way out.
I suppose it wouldn't hurt to have one if you want to pressure test?