Toilet tank slow to refill (bowl refills normally)...bad overflow tube?

Question

This is definitely a conundrum: not even our local hardware store could figure this one out! So, here goes:

We have a fairly new one-piece toilet in our guest bathroom that now takes forever to refill its tank! Note that there isn't a problem with the bowl refilling...that fills up fairly normally and rapidly. Also, this is a relatively recent change: this toilet actually used to be the fastest flushing toilet in the house.

Here is what I checked:

1. A visual inspection has uncovered no cracks/leaks from the tank portion of the toilet.
2. No problems with the flapper valve (we aren't getting plagued with random "ghost flushes", and the flapper appears to be seated well and sealing properly on each flush).
3. The water valve is fully open.
4. Just for the curious: the other toilet continues to flush normally.

Here's where the puzzle comes in: based on all of these observations and watching the problem toilet in action, it appears that the problem is the overflow tube, which I have never heard of (nor anyone else). The fill tube running from the fill valve is stationed to run water down the overflow tube--as I understand it, this is normal and is what allows the bowl to refill. But when flushed, it takes over four minutes for the tank to fill.

Here is another reason I suspect the overflow tube: it just so happens that the clip holding the fill tube in place over the overflow tube is wearing out. One time when I had the tank cover off and was repositioning the refill tube back in its proper place, on a whim I decided to hold the refill tube outside of the overflow tube, so that it would send its water directly into the tank, and flushed to see what would happen. The toilet bowl and tank filled rapidly--as one would normally expect--and shut off promptly.

What in the world is going on here? I appreciate any serious guesses!

Answer 1

The overflow tube drains directly into the bowl, not the tank. The only way I can think that it would prevent the tank from filling is if it was cracked or had a hole in it and allowed tank water to drain into the bowl. If this was the case, you would notice the fill valve cycling if it was a slow leak or never shutting off if it were a large leak. The reason the tank fills quickly when you divert the bowl refill tube into the tank is that you are simply not splitting the water from the fill value between the tank and bowl any more.

It sounds like your fill valve assembly is the problem. The fill value has 2 outlets, one that directs into the tank, and the other that sends water into your bowl refill tube. My best guess is that something inside of the fill value got clogged with sediment, hard water deposits, or something else that restricted it. These are relatively cheap to replace and likely not worth the time to clean them out in my opinion.

Answer 2

OK read your symptoms when looking for the cure to my similar problem.

Same thing exactly happened to me on a one piece Kohler fairly new unit rarely used. I found that there is an orange insert flow restrictor that blew out of its proper location ( at the barbed connection fitting on the tank fill valve for the bowl fill tube ) and was found in the flex tube. This allowed like 90% of the tank fill water to go wastefully into the bowl causing noise and very slow fill. I roughed up the exterior of the found restrictor and shoved it back in place. I also put a small zip strap on the hose near the barbed area. Back to normal now.

I only thought to look in the hose after reading the instructions for a replacement Kohler fill valve. It talked about installing the correct size restrictor of the 4 different sizes included with the new valve.