The problem is not foam getting into the output line. The problem is HHO gas is STORED inside the foam and can not be put to good use.

Eventually the bubbles in the foam gather, burst and release some HHO gas. This situation means that from the time the unit is turned on to the time that you start getting usable HHO gas that there is a significant delay.

An anti-foaming agent might be able to minimize this delay.