Waterway Poly Storm Jet Diffuser - 218-4000
Low alkalinity, pH or calcium can cause jets to deteriorate. Replacing only the diffuser is an option if the original diffuser is in good condition but the tabs holding the jet in are broken. If the diffuser itself is in bad shape then the jet bearings are likely failing as well. White residue flaking off the diffuser is likely plastic from the diffuser instead of scale. Replacing a diffuser in a situation like this will buy some time but a full jet replacement will not be far behind.