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I have three toilets that all flush slowly and incompletely. I've adjusted the chain to ensure the flap raises completely. I've raised the float to ensure the tank fills nice and high. Yet I have this nagging issue on all my toilets. It often takes multiple flushes to clear simple waste and toilet paper, never mind the "hard" stuff.

All the sinks and tubs drain well, no issues. I'm wondering if the age of a toilet can be a factor. All of my toilets are from the mid-eighties. I'm getting to the point where I just want to replace thm with some water-saving toilets but it would suck to have the problem persist.

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Do you live in a hard water area? There might be water deposits clogging the nozzles underneath the rim. I've used vinegar to clean water deposits; lots of people on this site swear by CLR though I don't know if it would be safe in the toilet tank... maybe turn off the water, hold the flapper open and pour some in directly? –  Niall C. Sep 17 '11 at 0:44
I live in Minnesota, have city water, and no water softener, I'm not sure I would really recognize hard water without serious stains in my showers. I'm curious, how does the amount of water coming from under the rim affect flushing? –  allnightgrocery Sep 17 '11 at 1:21
I believe it works by keeping the siphoning action going until everything in the bowl has been sucked past the curve in the waste pipe. Less water means air gets into the pipe so no siphoning: en.wikipedia.org/wiki/Flush_toilet#Siphoning-toilet –  Niall C. Sep 17 '11 at 1:31
septic, or city sewer? –  Tester101 Sep 17 '11 at 2:01
We have city sewer. –  allnightgrocery Sep 17 '11 at 2:08
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4 Answers

up vote 7 down vote accepted

I picked up some CLR and scrubbed all the jets under the rim. I even ran some through the tank - open flapper so as to minimize contact with the rubber and plastic. Using a mirror and a small piece of wire I was able to clean out a few stubborn holes.

All toilets were able to take a steady volume of water from a bucket without issue. This lead me to do a little more research. What I found was the hole at the bottom of the toilet that forces water down the drain is actually more susceptible to clogging and plays a larger role in the syphoning action. All three toilets had significant mineral build-up in this hole. A few minutes with my finger was able to clear out quite a lot. Some careful work with a small l-shaped alan wrench brought me the rest of the way home. Whammy!

The two younger toilets now flush like a champ. The oldest was so badly plugged I'll be needing a replacement. I'm gonna try a little soaking with CLR to see if it'll free up but I'm expecting a trip to the hardware store.

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To isolate the problem to the toilet internals and not any other plumbing, fill a large bucket (5 gal would be more than enough) with water and pour it in the bowl as fast as it will take it.

If it drains quickly, just replace the toilet, since you were already considering it. I'm amazed at how well the newer toilets flush without using lots of water. Short of replacing the toilet, I like Niall's CLR idea. You could also check that nothing is blocking the flow under the flapper with your fingers.

If the toilet still drains slowly, then you have a blockage that may not be solved with a new toilet. It could be an improperly installed wax seal, perhaps the drain line isn't properly sized, or there's something that can be snaked out. It's also possible you could have a venting issue, but I'd expect bubbles, gurgling, or bad smells with your other plumbing if that were the case.

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Here's an idea. Get the rim dry and then cover the drain holes with duct tape. Pour in the clr and let it sit for a good while. Pull off tape and gauge improvement. I've got a similar issue in my apt and now have to burn up a Saturday tackling it.

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Check the venting. You have to have good vent in the drain lines or you're losing half of your flush power to the siphon effect from the trap and water remaining in the bowl after the flush. Newer houses are usually fine on this unless there's been some remodling done by someone who doesn't understand what the vent up to the roof are for.

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