Toilet Bowl Pan Collar Fitting : Must have Silicon Seal

Sometimes when someone flushes his toilet on the upper floors, pressure is created that can suck water from your toilet bowl into the sewage pipe. When that happens the water level in the bowl will drop so drastically that it leaves a gap in the "S" bend, allowing foul air from the sewage pipe to seep into your toilet.

So if your toilet smells bad, first check there is sufficient water in the toilet bowl. No, not in the cistern but in the toilet bowl itself. This water in the bowl acts as a barrier to foul air from the sewage pipe, and prevents any foul smell entering the toilet through the sewage pipe.

If the water level in the toilet bowl is high enough above the "S" bend, then you should suspect an unsealed pan collar as the culprit for the stink.

Now, what about the report that some people complained their toilets smelled after the HDB upgrading exercise?

I believe that had nothing to do with the replacement of the cast-iron sewage pipe nor with the removal of the air vent pipe. The reason for the stink was very likely due to the bad installation of their toilet bowl. It was likely cracks developed at the cement base of the toilet bowl when the sewage pipe was changed, and because the pan collar of the toilet was not properly sealed, foul air escaped from the sewage system into the toilet.

LESSON LEARNT:

Ensure your plumber applies a silicone seal around the pan collar when he first installs the toilet bowl. That is the proper and correct procedure to install the toilet bowl. In the west plumbers use a wax gasket to ensure an airtight seal between the toilet bowl and the sewage pipe.

Readers will recall that during the 2003 SARS epidermic, it was reported in Hongkong the virus spread from one floor to the floor below via the sewage pipe. Although details were not divulged in the press report, I suspect the leak was caused by improper toilet bowl installation.

When someone flushes his toilet on the upper floors, obviously the foul air carrying viruses and bacteria will be "flushed" into the toilet on the floor below through the unsealed pan collar. Hence the stink.

I would probably have remained ignorant today of how unsanitary my toilet installation was had I not experienced the stinky toilet bowl problem.

Now, even if you have a toilet bowl that is completely sealed so that no air could escape from the chamber once the toilet is cemented to the floor, it is still advisable to ask your plumber to apply silicone sealant to the pan collar. Otherwise you risk allowing viruses to enter your toilet each time someone on the upper floors flushes the toilet.

As we know, cement is porous and over time will develop cracks so that most people will find their toilets stink after some years, especially for those with unsealed pan collars. You can prevent the stink by getting your plumber to apply silicone sealant to the pan collar during the initial installation of the toilet bowl.

Why risk your family's health?


POSTSCRIPT: Public health was at risk so I posted the issue on a forum, see below:

A friend pm'ed me asking why apply silicone sealant when the plumber already used white cement to seal the toilet bowl to the floor?

Well, the silicone sealant is applied to the pan collar -- the piece that is connected to the sewage pipe hole. If the pan collar is not sealed, foul air (and soil too) will seep into yr toilet bowl chamber due to the air presure at work.

Like others, I did not ask my plumber to seal the pan collar when he first installed the bowl. After installation, my toilet smelled badly, particularly when someone on higher floors flushed the toilet.

My toilet was a 1-piece design, and had 2 rectangular holes at the back of the toilet bowl. Hence I could detect the foul smell. More importantly, I realized the risk I was putting my family to, breathing in bad air, particularly bacteria and viruses from sick neighbors upstairs after they had flushed the toilet.

If not for the toilet design I had chosen, I would not have detected the foul smell, and the problem probably would only surface several years later.

You don't get any foul smell if your toilet bowl has no openings and is fully sealed by the white cement onto the floor. But over time the cement will develop tiny cracks, that is when you begin to detect foul smell from the toilet bowl area. That happened to my old toilet (after 5 yrs), although at that time I did not know what caused the bad smell. Maybe the earthquakes from Indonesia over last 2 yrs was a contributory factor, causing tiny cracks in the cement to appear, thereby allowing foul air to seep into the toilet space?

Anyway, when my plumber told me he never applied silicone sealant to the pan collar I realized probably all plumbers in Singapore also install toilet bowls without applying silicone sealant!

That is very unhygienic. Ask yr plumber if that is true. Probably he will tell you he don't use silicone sealant for your toilet bowl's pan collar too.

With unsealed toilet bowls we are probably breathing in all sorts of viruses and bacteria discharged from sick neighbors in the block without knowing it.

The HK health authorities at first were mystified how the SARS virus were spreading in the same apartment block. Finally they traced the spread to faulty sewage pipe.

The authorities did not reveal what caused the leak (in order not to spread public panic) but the culprit was the unsealed toilet bowl that allowed foul air (carrying the virus) to spread from one upper flat to another lower down. If the toilet pipe had merely been leaking water, do you think the affected flat owner would not have noticed that and left the leak unattended? Of course not! So I believe SARS had spread via the unsealed toilet bowl pan collar!

Now that my toilet bowl has been re-installed, there is no more foul smell !

So, please remind yr plumber to apply silicone sealant to the pan collar.

Possible Mistakes during Renovation Work

1. Misalignment of Rain Shower Arm

When the plumber installed the rain shower fitting, the misalignment was not apparent because the partition wall was then not tiled yet. It was only when the partition wall was tiled (on 24-Mar-08) that the misalignment became painfully obvious.

He should have, but did not, used a plumb line to determine the vertical alignment of the rain shower piping. Lapse of concentration, perhaps?

The tiler should have alerted the ID when he first noticed the misalignment, but did not. Maybe he was tired, because he arrived late in the afternoon at about 4 pm to finish the tiling of the partition wall. When asked by the ID, he maintained the owner saw the work and said nothing, so he thought the owner did not mind!

Mistake again!

After the tiler had completed the re-tiling, I noticed he had used his own initiative to further "adjust" the position of the pipe. The result was that now the rain shower arm was not vertically aligned with the concealed tap fitting, although the plumber had earlier already corrected the vertical alignment. Golly, what was the tiler thinking?

The tiler was apologetic.

I decided to let it pass as the misalignment was slight and not obvious to the casual observer. But it is a sore sight to my eyes!!!

I should have been there at the bathroom to supervise the tiler's work, and never took things for granted. OK, lesson learnt.

2. No hole for basin waste water discharge

Owing to a lack of foresight or focus, the tiler inadvertently cemented and covered the original hole in the bathroom floor that was meant for the hand basin discharge pipe. This was a major error, for the hand basin could not simply discharge its waste water into the bathroom floor!

And because hacking would damage the waterproofing layer in the bathroom floor, the tiler could not now hack the cement away to expose the discharge hole for the basin pipe.

Finally, a less elegant solution was to cut a hole in the plastic trap for the hand basin piping. Luckily there would be a partition wall to box up the ugly piping in the bathroom.

3. Side-by-side doors not top-aligned with each other

4. Other issues

Uneven skirting
Problem was caused by the uneven wall, and tiler simply cut and tiled the granite skirting to follow the unevenness. Neither the ID nor the owner were alerted. When the problem was subsequently discovered after an inspection, tiler had to remove the skirting, then hack away part of the uneven wall, and re-tile.

Fault was due to the uneven wall. Would be appreciative if tiler had alerted owner to the issue before tiling.

Wrong positioning of double socket point
Electrician will correct the positioning in subsequent days.

Internet piping in floor
Tiler did not discuss with owner or ID how the PVC pipe will be aligned with the skirting. Not a major issue, can live with it.

One instead of two feed cable for SCV
Electrician on his own initiative laid one SCV cable instead of two from the SCV junction box outside the flat.

Probably too late to lay 2 cables now as it will spoil the nice plastic trunking laid. Will try and see what can be done.

Mistake in light switches
Not yet discussed. Probably could change design of light fixtures to accommodate the switches.

Smelly toilet
Plumber claimed silicone sealant not normally applied to seal pan collar to the sewage hole when I asked him to apply. Should have insisted, because after installation the toilet still smells.

Self-applied silicone to the base, that reduced the smell somewhat but bad smell still detected.

Plumber will remove toilet and apply sealant to the pan collar, then re-install the toilet, if the smell persists after a few more days.

Completion delay
The window fabricator had already stopped taking orders when the contract was signed with the ID. That caused the delay, but the extent and severity of the delay on project completion was unforeseen.

Will know and prepare better in future.

Poor water outflow in toilet
Problem occurs in toilet, so is not severe as mop will be used to clean the toilet.

Thus can live with the problem, although problem should not have happened if tiler had correctly sloped the floor in the course of the tiling.

Fridge door unable to open fully to 270 deg
Fridge depth was 80cm and tiler created cement wall with same 80cm depth. As a result the fridge door could open only to 90 deg, whereas it must open to 150% or more to permit frdige shelving to be taken out for cleaning.

Wrong color for laminated flooring
ID asked the worker to remove the wrong color tiles and redo the laminated flooring. However the color was still too dark for owner's taste. Decided to live with it.

HDB approval delayed for hacking wall
The HDB officer claimed 10-day delay was caused by incorrect submission by the design firm. However, approval was given immediately when ID submitted correct drawings.