Gravity loop

I put in a gravity loop on my kitchen faucet and it works great. I have one problem though, and I don't know if it is associated with the loop. I have a water boss water softener. When I use the dishwasher or washing machine, I seem to run out of soft water. I do not have a check valve on the return line to the heater. Could this be the reason for running out of soft water?

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