Hiring the watchman's friend for concealed work
For a visible washer swap, an informal fix is a gamble with small stakes. For anything inside a wall, ceiling or floor, it is a gamble with someone else's apartment: no licence, no insurance and no traceable company means every dirham of consequential damage lands on you. The AED 50–150 saved is the most expensive discount in home maintenance.
Ignoring seized isolation valves until the emergency
Angle valves that have not been turned in years seize open, and you discover this at midnight with water spreading across the floor. Have valves exercised and the stiff ones replaced during any routine visit — the cheapest line item on the invoice and the one most likely to save your flooring.
Leaving no paper trail on anything involving water
Water-damage disputes in the UAE are decided by documentation: dated photos, licensed contractors' invoices, detection reports, in-app job records. Cash jobs with no receipt leave you unable to prove the work was done competently — or done at all — when an insurer, landlord or downstairs neighbour starts asking questions.