Every experienced fundi has a story about a “small” plumbing shortcut that turned into a flooded ceiling, an angry client and a weekend of unpaid rework. After years of supplying contractors across the region, these are the five mistakes we see most — and how to avoid every one of them.
1. Skipping The Pressure Test
Closing up walls before pressure-testing the pipework is the single most expensive gamble in plumbing. A test pump and one hour of holding 1.5× working pressure costs almost nothing; a leak discovered after tiling costs the tiles, the labour and your reputation. Test every circuit, every time, and get the client to witness it.
2. Undersized Supply Lines
Running 20mm pipe everywhere because it’s cheaper works in a bedsitter — not in a house with three showers. When two outlets open at once, pressure collapses and the client blames “your plumbing”. Size the main runs at 25–32mm and branch down to 20mm only for single fixtures.
3. Mixing Incompatible Fittings
A galvanised steel nipple threaded straight into a brass valve, PTFE tape doing the work a proper union should — mixed metals corrode at the joint, and mismatched threads (BSP vs NPT) weep forever. Stick to one fitting system per line, use dielectric or brass transition fittings where metals must meet, and buy pipe and fittings from the same standard.
4. Cheap Valves In Hard-Water Areas
The KSh 150 gate valve seizes solid within two years where water is hard. Quarter-turn ball valves with solid brass bodies cost slightly more and outlast the building’s paint. Put isolation valves on every fixture branch — the day a tap fails, the client shuts one valve instead of the whole house.
5. Unsupported Pipe Runs
Long horizontal runs without clips sag, pool water, hammer when valves close, and stress the joints at each end. Clip PPR every 50–80cm horizontally (closer for hot lines, which expand), and always within 30cm of a fitting. Pipe clips are the cheapest items on the invoice — and the first thing quantity surveyors cut.
The Common Thread
Every one of these mistakes saves a few hundred shillings on materials and risks tens of thousands in rework. Quality fittings, correct sizing and proper testing are what let you hand over a site and never get the angry call.
We keep contractors stocked with certified plumbing materials and pipes and fittings at wholesale prices — send us your materials schedule on WhatsApp and we’ll quote and deliver to site.