Mostreno · Guides · Plumbing

The plumbing guide.

What runs inside the walls, why the shower is weak, and the hard-water problem nobody mentions at quote stage.

01The two systems

Everything in plumbing is one or the other.

Supply is under pressure, waste runs on gravity. Almost every plumbing decision follows from which of the two you are dealing with, and most plumbing disasters come from treating them as one thing.

01
Supply
pressurised pipe bringing cold and hot water to every outlet. It is under pressure at all times, which is why a supply leak does damage quickly
02
Waste
open pipe carrying water away under gravity alone. It relies on fall, not pressure, which is why a waste problem is usually a levels problem
03
They are never interchangeable
supply pipe is small bore and rated for pressure, waste pipe is wide bore and rated for nothing
04
Both have to be set before tiling
chased into walls and floors, tested, and only then covered

02Pipe materials

What is actually inside the wall.

You will never see it once the plaster goes on, so it is worth knowing what was used. PPR is the Dubai standard for supply, and the joints are fused rather than threaded, which is what makes it reliable.

PPR (polypropylene)
Heat-fused joints, no threads to leak. The standard for hot and cold supply in Dubai.
PEX (cross-linked)
Flexible, runs in long lengths with fewer joints. Good for retrofits through finished walls.
Copper
Long-lived and rigid, but soldered joints and a price that moves with the metal market.
uPVC
Waste and drainage only, never supply. Solvent-welded, wide bore, cheap.

03Water heating

The single largest appliance decision in a bathroom.

In an apartment this is usually a tank in the ceiling void that you never see until it leaks. Its lifespan in Dubai is shortened by the water, which is why the choice and the servicing both matter.

Electric storage
A tank in the ceiling void that heats and holds. The default in most Dubai apartments.
Instant / tankless
Heats only as water passes. No standing loss, but it needs a heavy electrical supply.
Central plant
One system serving the whole building. Common in towers, and outside your control.
Solar thermal
Roof collectors with an electric backup. Villas only, and it pays back over years.

04Traps and drainage

The bend that keeps the drain out of the room.

Every fixture has a trap holding a plug of water. That water is the only thing between your bathroom and the smell of the soil stack. When a bathroom smells, this is almost always why.

P-trap
The standard. The bend holds water, and that water is what stops drain smell entering the room.
Bottle trap
Compact and tidy under an exposed basin. Blocks more easily than a P-trap.
S-trap
Runs straight down through the floor. Prone to siphoning itself dry, and now discouraged.
Floor gully
A trapped drain in the shower floor. Needs a removable grate or it cannot be cleared.

05Pressure, tanks and filtration

Why your shower is weak, or too strong.

Pressure problems are rarely the fitting. They are the supply, the pump, the valve or a blocked aerator, and each has a different fix.

Booster pump
Lifts pressure where the mains cannot. Villas and low floors. It should be silent, not audible.
Pressure reducing valve
Protects fittings from mains that are too high. A leaking mixer is often this, not the mixer.
Storage tank
Roof or ground tank with a feed to the property. Needs cleaning, and most never get it.
Filtration
Sediment and carbon stages before the fittings. In Dubai water this is maintenance, not luxury.

06Hard water

The Dubai-specific problem nobody mentions at quote stage.

Water here is desalinated and remineralised, and it is hard. It will scale your heater, block your aerators and mark your glass. Planning for it costs a fraction of replacing fittings early.

01
Dubai water is hard
desalinated and then remineralised, and it leaves scale on everything it touches
02
Scale shortens a water heater's life
the element furs up, efficiency drops, and the tank fails years early
03
It blocks aerators and shower heads
the usual cause of a mixer that has slowly lost pressure
04
It marks glass and chrome
the white film on a shower screen is limescale, not dirt
05
A softener or filter is maintenance, not luxury
cheaper than replacing fittings and heaters early

07Faults and what they mean

What the symptom is telling you.

Most plumbing problems announce themselves. Knowing which are local to one fixture and which are shared with the building tells you whether to call a plumber or the management company.

01
A damp patch on a wall or ceiling
supply leak under pressure. Isolate at the stopcock and do not wait
02
Drain smell from a bathroom
a trap has dried out or been removed. Run the tap, and if it persists the trap is the problem
03
Slow drainage everywhere at once
the stack, not the fixture. A single slow drain is local, several is shared
04
Gurgling from another fixture when one drains
a venting fault, drawing air through the wrong trap
05
Water hammer, a bang when a tap closes
pressure with nowhere to go. An arrestor or a PRV fixes it
06
Rising water bill with nothing visible
most often the toilet cistern passing water into the pan, silently

08What a proper job includes

The parts that are invisible afterwards.

Plumbing is the trade where the cheap version costs the most later, because a supply leak behind a finished wall damages everything around it. These are the things that should be in any scope in Dubai.

01
Use a licensed contractor
plumbing in Dubai must be carried out by a DEWA-approved contractor, and it matters for insurance
02
Pressure test before covering
supply pipe is tested and held before any tiling goes over it
03
Falls checked on waste
a floor gully with insufficient fall never drains properly and cannot be fixed later without lifting the floor
04
Building permission for stack work
jointly owned towers usually require notification before touching the soil stack
05
Isolation valves at every fixture
so one leaking tap does not mean shutting off the whole apartment
06
Know where your stopcock is
before you need it, not during
Questions

What homeowners ask first.

Do I need a licensed plumber in Dubai?

Yes. Plumbing work must be carried out by a DEWA-approved contractor. Unlicensed work can also invalidate your building and contents insurance if it causes damage.

How long does it take to replace bathroom plumbing?

First fix on a single bathroom is typically 2–4 working days, then second fix once tiling and finishes are done. It has to happen before tiling, not after.

Can you move the toilet or the shower drain?

Sometimes. Moving a fixture means moving waste, which needs fall and may need to reach the soil stack. In an apartment the stack position usually decides the layout, and moving it may not be permitted at all.

Why does my water heater keep failing?

Almost always scale. Hard water fixes deposits on the element, which overheats and fails. Flushing the tank periodically and fitting filtration extends its life considerably.

My bathroom smells of drains. What is it?

A dry or missing trap in nine cases out of ten. If running the tap for a minute clears it, the trap had dried out. If it does not, the trap is missing, wrongly fitted, or the stack is not venting properly.

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