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


In California the old style flushing toilets have been replaced by 1.6 gallon flow for some years. Starting in 2015 Santa Clara County Water District no longer subsidize this type. Rather 1.1. gallons is the style. Furthermore, many toilets have #1, and #2 option further reduce water waste.


Posted by Sam Shueh, mba, cdpe, reopro, pe ( (408) 425-1601) over 3 years ago

There are also those sink with a recycle drain into toilet. You wash your hands the grey water is being reused before it goes down the drain.


Posted by Sam Shueh, mba, cdpe, reopro, pe ( (408) 425-1601) over 3 years ago

I know the ins and outs of toilets.  I have found that the after market parts are garbage and the only real fix is a whole new toilet.

Posted by Chris and Dick Dovorany, Broker/Associate at Premiere Plus Realty ( Homes for Sale in Naples, Bonita Springs and Estero, Florida) over 3 years ago

Personally I really dislike it when the fill tube is out of place.

I like a properly filled pond.


Very kindly,



Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) over 3 years ago

Charles actually I don't find this boring. I now know why I was smelling sewer gases before the toilet was replaced!  I had no idea of why - but I did know it had to be gone.

Posted by Anna Banana Kruchten CRB, CRS 602-380-4886, Arizona's Top Banana! (Phoenix Property Shoppe) over 3 years ago

Charles.  This is vaulable information.  Some of us gals don't know about this tuff and now I feel educated!

Posted by Belinda Spillman, Colorado Living! (Aspen Lane Real Estate Colorful Colorado) over 3 years ago

Sam, attempts to use grey water have been around for a while---lots of concerns to consider when doing so

Chris & Dick, it does seem like that at times---but parts from the manufacturer of the toilet should be good to go

Croakster, it would appear that the fill tube got stuck in you

Anna, thanks. Sewer odors in the home should be avoided for sure.

Belinda, thanks---always glad to help. :)

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) over 3 years ago

You got a nice semi-long blog post out of it, so not all is lost in that respect. Be well, my friend.

Posted by Laura Cerrano, Certified Feng Shui Expert, Speaker & Researcher (Feng Shui Manhattan Long Island) over 3 years ago

Laura, indeed true

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) over 3 years ago