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HDB Mandatory Water Proofing Test ... Please advise ...

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My HDB estate is currently undergoing Home Improvement Programme (HIP). HDB units (especially those just renovated their houses) who do not opt for toilet/bathroom upgrading must undergo a compulsory water proofing test. According to HDB, the toilet floor will be flooded to 2.5cm of water for 4 hours. If there is leak to the ceiling of the flat below then the water proofing test has failed.

We all know HDB flats are strictly residential. I can't think of anybody who bathe for a continuous long period of 4 hours and able to flood the toilet floor to even 1cm of water. The diameter of drainage outlet is so much bigger than diameter of shower tap. Water outflow is anytime faster than water inflow.

Is the criteria for HDB water proofing test a little too far fetched and UNREALISTIC.

Also, are water proofing membrane done by HDB authorised contractors designed to withstand 2.5cm of water for 4 hours; because I never hear it mentioned when I talked to renovation contractors and it was never even in the terms and conditions.

I have people in other forums insisting this is standard test. Since this criteria was never mentioned or noted in renovation contract, can we assume it is standard HDB requirement and so is IMPLICIT in the agreement. And suppose water test failed, can we get contractor to compensate/foot cost of repair ?

I hope HDB, MND, URA, building professionals, and knowledgeable people can kindly contribute, comment, and advise on this matter.  Thank you.


PS: I am not so IT literate and my friend help me post this article. If there is a proper forum to raise this issue, kindly help me port this over or do advise. Thank you.

Edited by goldenchasis
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I was in the same situation as you several years ago when my previous HDB estate was undergoing HIP. I had written to HDB and ST forum about this and had also offered to have a written agreement to foot any costs involved in repairing the floor if leakages happened in future but HDB said there's no such policy. 

basically as long as the water test fail, meaning water seepage/marks can be seen (need not be dripping water) on the downstairs neighbor's ceiling, you WILL need to renovate the toilet even if it's just a tiny seepage. You must understand that when you "BUY" a HDB flat, you are actually leasing the flat from HDB for the balance of the 99years that is left on the flat. So as the actual "owner" of the flat which you have leased from, you are subjected to their terms and conditions of living and maintenance of the flat which includes this HIP toilet renovation.

The water test is designed such to cater for situations where there is water pipe leakage/burst and also the drainage pipe choked for a period of time which will cause flooding in the toilet. Hence the 2.5cm of water for 4 hours.

If you had done your renovation recently and the toilet test failed, it's up to you to see how much warranty your contractor had provided you for the toilet renovation. From my understanding, the toilet works by HIP contractors will have a 5 years warranty against leakages.

Just for info, when the HIP contractors do the test, they will flood your toilet and use those blue pills for WC to colour the water so that the seepage (if any) can be seen clearly downstairs. if your toilet fails the initial test, you have several options.

1. do the toilet renovation following the HIP

2. get your contractor to renovate the toilet and after renovation, get the HIP contractors to perform water test again

3. get your contractor to waterproof/fix the leakage then do the water test again

Basically you have 2 chances to prove to HDB that your toilet does not leak at all. if it leaks, you are given the option to go with HIP works or engage your own contractor (subject to water leakage tests again afterwards).

for fixing of leakage, there is an option to inject some sort of sealant into the ceiling downstairs. this will cause some inconvenience to your neighbor and will also need their approval since workers would need to go into their house. Cost wise would end up about the same as doing the entire toilet under the HIP package.

Luckily for me previously, the seepage was in a small area which normally would not be wet (as we had an enclosed shower area and the seepage was outside this area). After doing some waterproofing of the toilet floor by applying sealant, we managed to pass the 2nd water test and avoided renovating our toilet.

Hope the above information helps. Good luck!


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Professionally speaking, the soak test should last for 24 hours instead of 4 hours for a more conclusive finding. The timing depends largely on the concrete permeability and thickness. You may read Darcy's Law for further understanding.

Anyway, HDB Quality Group must have some certifications reaching the '4 hours' conclusion.

If one can observe damp patches on the soffit within 4 hours, the 'leakage' is very serious and need immediate action.

Water can be retained in the slab/concrete and slowly spreads horizontally and vertically, over months or even years and the damp patches can be observed on the soffit....(in another word - HDB is signalling 'Pls settle with your neighbor next time and don't look for me', if you opt out)

It is often found the 'leakage' happens at floor trap area and stackers' (we don't call pipes) perimeter. The water 'travels' along the stacker wall (if waterproofing material not sticks to the stacker, or tall enough with the tile.....) then, i would say 'good luck'.

I personally told the ID and supervised the contractor on this very particularly, in late 2009. 2016, HIP came, i opted in just to pleased my neighbour down stair tot there was a 'downgrade' in everything in the toilets.


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Planning to renovate the bathroom and changing the floor tiles. But I've also heard how some of my friends did and there's leakage and it's a hassles to settle it. Any recommendations for a good contractor? 


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