Saw this inside the lift at Toa Payoh Rise when we visited Creamier for ice cream.
My partner told me that this is much cheaper than going to a car wash which can cost at least S$10-12.
But he said that not all HDBs have the full set of equipment so you need to know where to go. He added that not all multi story carpark washing points are equal. They are tendered out to different vendors. And depending on the vendor, you get different facilities. One thing that is consistent though are the prices for the water and jet spray.