Seattle Home Inspector's Blog


It just doesn’t get any more boring than this!

How many of you know what your toilet tank bowl fill tube is?

I can see by the non-existent forest of hands, many of my readers have no clue what I am talking about.  Of course inspectors and plumbers do not count--I can see them waving frantically.

The bowl fill tube does just what it says.  It is in place so that the toilet bowl will refill to the proper level after the toilet is flushed. 

This is not too big of a deal because very few toilets in my opinion flush “properly.”  A properly flushing toilet will literally siphon all the water all out of the bowl, so some means of filling the bowl is necessary in order to prevent sewer gases from entering the home.

Toilet tank fill tube

Because of drain and vent installation issues and the age of some toilets, many toilets do not flush away all of the water and filling the bowl is accomplished by water running back into the bowl either around the flapper before it starts seals “completely” or even before the flapper can get to the place where it eventually will seal itself completely.

Regardless, in order to ensure that the bowl refills to proper levels the fill tube must be properly connected to the overflow pipe inside the tank and there must be an air gap.  Without an air gap, water can supposedly siphon continually into the overflow tube making the toilet run intermittently.  This tube should not merely stick inside the overflow pipe to extent that the end would be below the water level in the tank. 

In doing a little research for this post, I checked my own toilets for how all this functions in the real world and found that my basement toilet has had the tube stuck inside the overflow well below the water line for over 15 years and it does not run intermittently.  However other brands of toilets may behave differently.

With both of my toilets, if the tube is allowed to aim inside the tank and not inside the overflow tube, the bowls do not fill quite to the same level as they would if it was inserted into the tube, but the difference seems barely enough to make much difference. I must add that my toilets are older and there are both drainage and venting issues typical of the age of my home and that would not be typical of a modern plumbing system.

In fact, aiming inside the tank helps the tank fill faster wasting less water than the amount wasted maintaining the water a mere ¼” higher in the bowl. On both of my toilets, the amount of water that runs to the bowl is one quart.  That is one quart of wasted water per full flush to maintain the water in the bowl ¼ to ½ inch higher.

This fill tube helps to “guarantee” an appropriate level of water in the bowl, and any perceived wasting of water may be necessary to achieve that level of safety.  The more modern the toilet, the better and quicker the flap will seal, and the better the drainage/venting plumbing will be installed. This will likely result in the fill tube being properly installed into the overflow tube being necessary.

Fill tube disconnected

If the water level in your toilet bowl is not as high as it once was, perhaps the fill tube is no longer in its proper position.

Charles Buell, Real Estate Inspections in Seattle

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Seattle Home Inspector


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Comment balloon 9 commentsCharles Buell • July 24 2015 11:14AM
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