Walmart Toilet Chemical vs. RV Dealer Toilet Chemical

Chemicals are a waste of money. The only stuff I put in the black tank is to make the inside slippery and to help break up solids, and hand dish detergent or water softener are perfect for this. The usual chemicals sold with formaldehyde are not septic tank friendly.

As for vent caps, so far the best I've seen is a small fan powered by a solar cell. This helps suck out air regardless if the rig is parked or moving, and regardless of wind speed.