Weak flush on dual-flush toilet

Old 03-09-19, 01:26 PM
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Weak flush on dual-flush toilet


Trying to help my dad solve a problem with his toilet. He has 2 dual flush toilets that appear to be of same/similar make/model. One flushes well, one doesn’t.

They are dual flush, with a the two button canister type flush valves.

Water level is just below the overflow drain pipe. Tank seems to drain almost fully when using “solids” button.

The siphon action seems week. Vinegar has been run through the tank and bowl.
I know a certain generation of dual flushes were pretty weak in general. Wondering why one of the works well and one doesn’t. Haven’t resorted to pulling toilet yet in search of rare obstruction.

Couple of questions:

1. Can you lengthen the over flow drain pipe so you can have more water fill in the tank before the flush? Maybe a larger flush would help.

2. Is the canister valve adjustable in any way? I see numbers written on the side up to 17.....what do these mean?

Right now, it’s almost useless. Flushing urine alone with button #1 doesn’t flush all the urine. Flushing solids is almost impossible.

Any advice or poor design?
Old 03-09-19, 01:44 PM
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First, check to see if the problem toilet can be made to flush well. Get a bucket with a gallon or two of water. Quickly pour the water into the center of the bowl. Does this cause a good, strong flush or is it a slow, weak flush? If it's a poor flush with the bucket test then the problem is likely in the drain somewhere. It could be a partial clog in the toilet's trap or in the drain piping. If the toilet flushes well with the bucket test then you need to look at the toilet for the problem.

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