I have a toilet that flushes reliably IF I dump a quart of water into the bowl after pushing the handle down to flush the toilet. Otherwise, the water swirls lazily around in the bowl but doesn't get the real work done. I went on the roof & the stack pipe is not blocked.

A plumber came & snaked it. Then he removed the toilet, took it out back & snaked it backwards, flushed water through it, etc. etc. He put all new insides in the tank & reinstalled the unit. Nothing is changed.

I have a 30' pine tree in the front yard. I bought some stuff that says it will remove tree roots, but the plumber says not to put any chemicals down the toilet.

Any idea what the problem could be & what else I could try? Thank you.

You say it flushes reliably if you pour a quart in the bowl after flushing. What happens if you pour a gallon in the bowl with out flushing?

If I pour a gallon in the bowl without flushing, the water level raises temporarily, then goes back down to its original level in a few seconds. No flush takes place.

I should have said rapidly, like dump a gallon out of a bucket. Is toilet a siphon jet type, has a hole about 1" in discharge.

By siphon jet, I'm thinking you mean a toilet with a small hole at the bottom, in addition to the main hole that everything is supposed to disappear into. I don't have that.

I just dumped a gallon of water into the bowl rapidly without flushing, the water level lowered temporarily, then went back up to its original level in a few seconds. Again no flush took place.

Hope this helped.

Sounds like you have a partial blockage in the toilet drain pipe. Should be close. Try clearing with a toilet auger. If that doesn't help you will have pull toilet and snake the line.

Already did both things that you suggest, before posting. Since they didn't work, what's next?

Sorry, I should have reread your original post. Is water level in tank at it's maximum?

No, it's about an inch short! How do you change that?

One inch below the top of the overflow tube is about right. If you have a fill valve like on the right, some have a little spring clip on the brass rod that connects the float to the lever. You compress the clip and slide the float up slightly. Some, more recent models have a long plastic screw as a rod that you can turn to adjust the float.
If you have a ball cock like on the left, grasp it the brass rod with both hands and straighten it slightly.

What happen if you hold the flush lever down? Does the toilet flush properly? If so, look at the length of chain between the flush lever and the flapper. There should be just enough slack to insure that the flapper closes. Too much slack and the flapper will not be puller up far enough and may close too soon.

My toilet insides are like those in the righthand picture. The water is 2" below the top of the overflow tube, 1" below the line labelled "water line". Stunning full-color shots of the inside of my toilet are attached for your viewing pleasure.

I think I have the long plastic screw kind of adjustment, but I can't figure out which way I'm supposed to turn it, as nothing seems to happen either way. It did seem like the flapper quit prematurely, so I shortened the chain, but then the flapper didn't close entirely. So I put it back the way it was & now it closes with about 1 1/2" of water still in the tank. The toilet does not flush properly if I hold the lever down.

The water level seems a bit more than an inch short now, after my fiddling around.

OK looks like you got good water level and flapper acting about right.
You should have plenty of water and fast enough to make the toilet flush.

I'm back to a partial blockage.

Bear with me for a little principle of operation here. If you add enough water to the bowl, fast enough to cause the water level to rise above the trap that is built into the toilet, the water fills up the discharge pipe and begins to flow out. The water flowing down the pipe pulls all the remaining water in the bowl behind it. This siphoning action continues until air enters the pipe when the bowl is empty.
If there is a blockage or a partial blockage in the pipe that prevents the water from flowing freely the siphoning action stops.

Pull the toilet and snake again. I don't see any other answer other than a partially blocked pipe. I don't know what kind of snake the plumber used but it is not unusual for a small drain snake to pass a partial blockage or to pass through.

You could try a small drain snake again but you may have to rent a sewer snake. You could have something lodged in the drain and the toilet flush all right for a few times. Then have paper and solids get caught on what ever is lodges in the pipe and restrict the flow.

Got any small children?

The water level is still an inch below where it's supposed to be. Could that do anything?

Reason I returned to that is: this plumber used a commercial snake and a smaller snake and a few tricks only someone who's been doing it for decades picks up. He spent almost a whole day on it before putting the toilet back. He got out two of my husband's catheter caps, but that made zero difference. If something's in there, I don't believe snaking will remove it.

One other question: Could there be roots beyond the bathroom causing these symptoms? I bought some copper sulfate root killer, but the directions say to put it in the toilet & the plumber was dead set against putting chemicals in there. What's your opinion?

Also, which way do I screw the rod to make the water level higher?

Turning screw clock wise should raise the float and raise the water level.

Copper sulfate is commonly used to kill roots. It is a temporary measure. It doesn't clear the root just kills them. They always come back. You do this as a temporary measure until you can dig up the sewer line and repair the break. What makes you think you have roots? Your blockage sounds closer than that. If you could flush one or twice and then have a back up that would sound more like a blockage in the sewer line outside.

I would think your sewer line would be below the frost line. That should be pretty deep in your area. Don't know if tree roots would even grow that deep.

I turned the screw clockwise until the water filled to the line - and viola! It flushes.

The idea of using copper sulfate to kill roots is because I have a 30' pine tree in my front yard, & my neighbor just had his front yard dug up to repair a breach in his sewer line.

Your comment about the frost line brought an "aha!" moment to me. I've seen pine trees that have been uprooted by storms. Their root system is really shallow. I think putting copper sulfate in the sewer line would have the same effect on roots as putting dollars bills in the sewer line. Thanks!

My toilet flushes. I'm a Happy Camper. Maybe one day soon I will take the flapper chain in one link so that the flapper closes just a tad later. Not sure I could handle perfect flushes every time, though. Thank you so much - janet

Congratulations Janet.

The flapper chain should have just enough slack to insure that the flapper closes properly. There are also flappers that have an adjustment mechanism. They work bu adjusting how fast the air trapped in the ball escapes. You can make them close faster than a normal flapper but you can't make the close slower than a regular flapper.
Come to think of it, you may have one of those, if so discard it and put in a regular flapper.

I have one that most repair plumbers miss.. Look down at the bottom of the bowl. If there is a small hole, then that is a jet that starts the syphon action. If it's clogged the water will just swirl around and slowly go down leaving solids behind. Take your finger,(UGH! ) and run it around the inside of the opening. Over the years minerals build up and cut down on the syphon (flush) action. If it is rough or you feel build up, take a table knife and put a bend in it to get around the curve in the bowl and chip and scrap it clear. Next take a coathanger and clear out the holes around the rim. They start the swirling action. And last, check the water level in the tank. It should be 1/2" below the top of the over flow tube. And speaking of the overflow tube, Make sure the small 1/8" tube from the ballcock to the white overflow tube is connected so it discharges in it and that it's flowing when the ballcock fills. This is what raises the water level in the bowl. For a good solid flush they all have to work together. Hope this helps and thank you for rating my reply.. Tom

Will do, thanks.

Please let me know if it works for you. Good luck, Tom