Despite many pitches falling to the icy and frosty conditions, Davidson Park played host in wet, rainy conditions.
United took an early lead when Stuart McMullan manoeuvred to score a solo effort.
Ballynahinch doubled their lead after Lee Maxwell wriggled into the box to score, with Ross Murray following up to make sure it had crossed the line.
Thomas Rodgers was upended inside the box giving designated penalty taker, Stefan Graham, the opportunity to make it 3. The United captain duly dispatched.
It looked as though the away side were home and dry, despite the torrential conditions.
However, Ballywalter pulled one back just before the end of the half.
Buoyed by that, the second half proved much more difficult for Ballynahinch.
The home side then bagged another two to draw level as Ballynahinch failed to get back to the level required.
Ballywalter added another two without reply to pick up all three points despite being three goals down after a complete catastrophic capitulation from Ballynahinch, in what could be a decisive fixture come the end of the season.
The two teams go head-to-head again this weekend at The Millbridge.
Line up: Stefan Graham [C], Thomas Rodgers (Jamie McNeill), Scott Brashaw, Chris Coleman, Richard Annett, Stuart McMullan, Ronnie Johnston (Andrew Shannon), Greg Hall, Glenn Bennett, Lee Maxwell (Scott Cheevers), Ross Murray.