Captain Jimmy Tupou scored the first try of the match, after 46 minutes, between the uprights, and Fifita pounced on a Waikato error from a Judd box kick to bolt 40m. Jordan Taufua scored the third at 75 minutes with a typical bustling charge.
Waikato, under the cosh from referee Richard Kelly for multiple infringements, could get little going. Lock Peni Iowane was binned for a no arms tackle. Damian McKenzie kicked three penalty goals, but missed two.
Counties Manukau had a late defection in No 8 Maama Vaipulu. They were able to field two fetchers in Sam Henwood and Onosa'i Auva'a, while Jordan Taufua has played openside this season. That Steelers loose trio caused issues at the breakdown for the home side.
Prop Sam Aiono was also a late sub for Jarrod Firth, but the most intense scrum battle of the night was Ben Tameifuna, in his last home match before departure for Parisian club Racing-Metro, against Pauliasi Manu. The latter had the edge.
Waikato centre Anton Lienert-Brown played his blazer game but had precious few chances to show his attacking wares in such weather.
Waikato can salvage their season, and perhaps ensure their Premiership status, in a Ranfurly Shield challenge next Friday in Napier, while the Steelers host Auckland in Pukekohe next Saturday night.
Counties Manukau 30 (Jimmy Tupou, Sione Fifita, Jordan Taufua, Frank Halai tries; Piers Francis 2 con, 2 pen) Waikato 9 (Damian McKenzie 3 pen) Halftime: 6-3 Counties Manukau