How to do a drainage test at BTO key collection (floor traps, ponding and leaks)

Hollow tiles get most of the attention at key collection, but water problems are the ones that cost the most later. A floor that slopes the wrong way, a slow floor trap or a pipe that weeps under the sink is easy to miss on a dry floor and hard to fix once your contractor has started. A simple water test takes about 15 minutes and shows you most of it.

What you need

• A pail or large bottle (a 5-litre bottle works) and access to a tap. You'll need your SP utilities account opened before key collection so the water is on.
• A torch, for looking into floor traps and under sinks.
• A marble or small ball, to see which way the floor slopes.
• Painter's tape and a marker, to number anything you find.
• A dry cloth or tissue, to wipe joints so new drips are easy to see.

Where to test

Test every area with a floor trap: each bathroom, the kitchen, the service yard and the balcony or ledge if your flat has one. Do the same steps in each place.

The test, step by step

1. Look first, while the floor is dry. Check the floor trap cover sits flush with the tiles and doesn't rock when you step on it. Shine your torch inside: it should be clear of cement, tile grout or debris left by the builders.
2. Roll a marble. Put it down at a few spots around the room. It should roll towards the floor trap. If it rolls towards the door or stops in a corner, that part of the floor isn't sloping the right way.
3. Pour water from the far corners. Pour a pail slowly from the corner furthest from the trap, then from the other corners and along the walls. Water should run steadily to the trap.
4. Wait five minutes, then look again. A thin wet film is normal. A puddle that stays, or water sitting in a corner or along the edge of the door, is ponding. Take a photo with the tape number in the shot.
5. Watch the trap. Water should disappear quickly without gurgling back up. If the trap fills and drains slowly, it may be partly choked.
6. Check the doorway. Water must not flow over the threshold into the corridor, bedroom or living room. Pour a little near the door and see where it goes.

Taps, sinks and pipes

• Run each tap for a minute. Look for steady pressure and no spitting.
• Wipe the joints under the kitchen sink and any basin dry, run water for a minute, then wipe again with a tissue. A wet tissue means a slow leak.
• If a WC is installed, flush it a few times and check the base and the pipe behind for water.
• Fill the sink partly, then let it drain. It should empty without bubbling up in the floor trap nearby.

Look up, not just down

Ceiling leaks usually come from the bathroom above, and they may only show after the upstairs neighbour starts using their shower. At key collection, check bathroom and kitchen ceilings for stains, bubbling paint or damp patches, and lift the access panel if there is one to look for wet pipes. Take dated photos of the ceilings even if they look fine: it gives you a "before" record if a stain appears later.

How to report what you find

1. Number every issue with tape and take one close-up plus one wider photo that shows where it is. For ponding, photograph the puddle with the tape beside it, since the water will dry before anyone else sees it.
2. Describe it in plain words: "Common bathroom, water ponds in corner beside door after 5 minutes" is more useful than "drainage issue".
3. Submit your list to the Building Service Centre (BSC) with the defects feedback form from your key collection pack or HDB's online service. Try to do it within the first month, and before your contractor starts work.
4. Ask for a re-test at the joint inspection. Bring a bottle of water and pour it in front of the BSC officer, so they see the same thing you did.

Why it matters before renovation

Once a contractor lays new tiles, builds a vanity or changes anything in a wet area, it becomes hard to show that a drainage or leak problem was there from the start. HDB's maintenance guide notes that new flats come with a 5-year warranty on ceiling leaks, but that this warranty ends if the floor tiles are changed or the waterproofing system is tampered with. Read HDB's renovation guidelines before making changes in bathrooms, and get the original defects fixed first.

Check again before the DLP ends

Some water problems only show up with daily use: a slow drip under the sink, a stain on the ceiling, a floor trap that smells. Repeat the same test around month 10 or 11, before your 12-month defect liability period ends, and report anything new.