incomplete flush in all our toilets - intermittent problem

[kara]

When we flush our toilets (not just one) the water does not flush all the way down. It drains most of the contents, but it does not totally drain and you dont get the girgle at the end. Sometimes, holding the handle down the entire time the water drains works. However, not always. Also, the problem is not consistent. When we bought our house 8 months ago we noticed it in the basement and assumed it was a flapper problem. Then as time progressed it has intermittently happened to all our toilets. The house (and toiletes, I assume) are about 20 years old. Any idea what could be causing it?

[Terry]

If there is something in the trapway, it will slow down the siphon action.

Some brands and models of toilets are better than others at keeping the trapway clean and usable.

Most any toilet will work well enough, if all things are clear.
But if you do have something there, it will need to be:
washed down,
augered out,
or pulled out.

[kara]

it isn’t just one toilet which is why it is confusing.
do you think it is indicative of a larger problem, since it affects all toilets. Is there anything with a central pipe that could be affected?
Also, it is not consistent. it comes and goes.
I initially though something with the water pressure, but my husband nixed that idea.
Thanks, kara

[Cass]

Is it just you and your husband in the house or do you have kids?

[kara]

It is just us, no kids.

And I dont seem to find any relationship between showers/sinks, ect running at the same time, either.

Thanks for your help!

[RRW]

Septic Tank or Municipal Sewer?

[plumber1]

Just for giggles take the lid off the tank and make sure the water level is about 3/8" below the overflow pipe and that there is a good flow of water from the refill tube going into that overflow pipe so that the toilet bowl is always filled to the highest level.

I have seen it where the customer or someone lets the refill tube just help fill the tank and is not directed into the overflow. If the water level in the bowl is low, the toilet won't flush well.

This kind of condition allows the toilet to flush properly every other time or so.