Porta-Pak by Walex is a trusted RV toilet and black tank treatment. Each water-soluble, scented packet provides powerful odor control and waste breakdown. Just drop a packet into your toilet, flush, and enjoy up to 7 days of freshness. Porta-Pak treats black holding tanks from 2.5 gallons up to 40 gallons. It works in all weather conditions and is formaldehyde-free. The resealable bag contains 10 mess-free packets for easy use. Keep your RV tanks clean and odor-free with Porta-Pak, the ultimate choice for RV waste treatment. Refreshing Clean Linen fragrance.