The Omnipure Q5421-P is a 10 micron Carbon Block Water Filter with Phosphate Scale Inhibitor. The Omnipure Q5421-P Carbon Block Scale Inhibitor water filter is very user-friendly. Replacement of the spent media bed is done quickly by detaching the filter body from a permanent head with a twist of the wrist. The new Q5421-P filter body is just as easily threaded into the head and the replacement is then complete. The Omnipure Q5421-P is also available with the optional Twist Tap in-head valve system, which automatically turns the supply water off when the body is disconnected from the head. The Omnipure Q5421-P can be used as a pre or postfilter for Reverse Osmosis Systems, beverage equipment, drinking water fountains, ice machines, and other point-of-use applications. The Omnipure Q5421-P GAC water filter is a granular activated carbon block filter with phosphate used to reduce scale, taste, odor and chlorine taste and odor.