Toilet tank hissing sound and slow leak?

D107

I had just congratulated myself (HO) on setting the blue adjustable Toto fill valve at the correct height so now the bowl and tank fill to proper level. (I had also replaced the fill valve cap R528.) Flushes well and refills quickly.

A few days later I notice the tank water level goes down slowly and I hear a very slight hissing from the fill valve. I figure that would more likely be the 9-year old flapper leaking water but when I press flapper, hissing sound still there.

When I replaced the cap I didn't take the final step of cleaning the fill valve filter--usually at the bottom where it meets the water supply, if it even has one. Or I think if you remove the R528 replacement cap I've seen guys pull the assembly below it to reveal the filter. But an issue with the fill valve wouldn't lower the water level would it? Fill valve is 15 years old.

Now just flushed again and heard no hiss after it filled. Will have to check water level later. Perhaps when I rubbed down the flapper I dislodged some grit?

Larry Weingarten

Hi, If the flapper is black rubber, when you rub it with your finger, does your finger turn black? If so the rubber has deteriorated and needs replacing. I'd start with that and see if then the fill valve quits filling when it shouldn't.

Yours, Larry

mattmia2

some food coloring in the tank will tell you if the flapper is leaking. the water in the bowl will be colored if it is leaking. Put some food coloring in the tank and wait 20 minutes to an hour or 2 and see if the color appears in the bowl.


Most likely what is happening is the flush valve is leaking, the water level falls, the fill valve opens a little and makes noise as water passes through it to replace the water lost through the leaking flush valve.

Steamhead

mattmia2 said:

some food coloring in the tank will tell you if the flapper is leaking. the water in the bowl will be colored if it is leaking. Put some food coloring in the tank and wait 20 minutes to an hour or 2 and see if the color appears in the bowl.


Most likely what is happening is the flush valve is leaking, the water level falls, the fill valve opens a little and makes noise as water passes through it to replace the water lost through the leaking flush valve.

This.

Let us know how you make out.

D107

Thanks all. @Larry Weingarten flapper is toto orange and feels brand new. (and flapper chain has enough slack.)
@mattmia2 @Steamhead

Just inspected again an hour after new flush (no hiss then and tank water level was fine), now hour later water level has gone down, but not yet enough to activate fill valve; I expect that will happen shortly. Interesting how leaks can happen but the tank cover will muffle the sound and you'll never know.

1-If the flapper the only part of the flush valve assembly that can cause this? If those tank bolts were not tight enough? (One side wasn't fully tightened by original installer, but after I'd tightened it myself a little bit it pretty much doesn't move.) Should I just replace flapper first?

ChrisJ

When it's leaking, if you shine a flashlight down the overflow tube what can you see?

It's either the flapper, or the flush valve / overflow tube assembly, there's not much else there. If the new fill valve was leaking it would be all over the floor, not into the bowl.

At 15 years old I'd pull the tank and replace those gaskets as well as the flapper honestly.

ethicalpaul

Just a homeowner here, but I saw this once where the fill valve wasn't getting closed all the way by the float, so it was always leaking a little water by. The flapper was fine.

I applied corrective force to the float arm so it provided the necessary upward force to the fill valve (I bent the hell out of it)

mattmia2

If the tank bolts were leaking it would leak on the floor. Look closely at the surface of the flapper where it seals to the lip of the flush valve, usually you can see a circle where it seats with a little gap in it where it is leaking if you look at it at the right angle. As the plastic hardens over time it may not flex enough to seat properly or become to soft and not seat properly. Look for debris or damage to the seat and the flapper but it probably is just the flapper deteriorating.

mattmia2

Is it the right flapper for the flush valve? Especially if the arms are too short it can hang up and be held just a little bit open.

Larry Weingarten

Hi, Try this... Lift the flapper and run your finger over the surface that the flapper seals to. If you find any roughness at all, that could be the problem.

Yours, Larry

HomerJSmith

Do the red food dye first to see if the dye makes its way into the bowel. A full tank's water level should be about 1" below the top of the overflow tube.
It appears to me to be a one piece toilet. The flush assembly and gasketing is different on a two piece toilet. I run my thumb nail around the plastic seat to see if there are any grooves cut into it where water could seep out. I have also put thick silicone grease on the sealing side of the flapper. I like flappers with rigid arms and not silicone rubber arms like you have.
Put a little water in the bottom of the bowel even with the top of the drain weir (raise the flapper until no more water runs out of the tank). Add food coloring to the water in the bottom of the tank and let set for 12 hrs. If there is coloring in the bowel suspect that the flush valve gasket that seal the valve to the tank is leaking and not necessarily the flapper.

hot_rod

New flappers are very inexpensive😗
I always replaced both in a toilet rebuild to save recall trips

get the softer rubber built for aggressive water

Fluidmaster always had good quality kits
Look for a notch in the seat if the flush valve

D107

Thanks all. 2pc Toto CST743. So I carefully checked flapper and seat all around, like new.

@HomerJSmith If the flush valve gasket that seals the valve to the tank is leaking ––and not the flapper––wouldn't the water be dripping from the tank? Outside tank is bone dry. I'll try the food dye in tank first. Upon flush, water rises to 6.5" but eventually goes down to 6.25" or below before I hear fill valve. Fill valve might not kick in until it's down to 6". But ten minutes after the flush, water went down 1/8" which is fast. Wonder if cause is not flapper, is fill valve somehow siphoning water from tank back into supply?

This leak would explain to me why the tank was sweating so much internally the last few months, and mold was in the bowl where it had never been. Inside tank top was dripping. That constant influx of cold water could have caused condensation within the tank. (never saw it outside.) Don't think that would happen if siphoning/backflow was happening.

mattmia2

You're absolutely sure it is the right flapper for that flush valve because it looks awfully close to the overflow tube.

Was the pattern on the bottom on the bottom of the flapper where it seals continuous?

Dave Carpentier

Sure sounds like the flush flapper.
The chain from the handle shaft down to the flapper has some slack by the looks of it ?
Is the little ring/triangle that attaches the chain to the flapper free to move around ?

D107

Thanks @mattmia2 @Dave Carpentier as for the 'correct' flapper, I really can't say but there is no model # on it, but it's identical to the one on my other Toto--same tank--installed by different plumbers 6 years apart. Only model # I found was Toto 9AU056N which seems more like the original valve part than a flapper. The flapper lip seemed continuous but the seat on which it sits, while continuous, seems a little less prominent at the location of the overflow tube. It's all one piece obviously but it's possible that at that location the flapper could grow weak.

Also the angle that the flapper gets pulled at is not straight up like the other flapper we have. I probably can't change that angle unless I change out the entire flush valve, but I recall that plumber was careless in various ways. As far as I know these should be universal 3" flush valves.

But as old as they are, they're overdue for replacement. I'll try to find some food dye around and assume the most parsimonious explanation is the answer.

mattmia2

unhook it from the flush valve and take a good look at that little circle the seat has made on the flapper.

do the ears clip on the tube or is it all molded as one piece? it looks like it is contacting too far clockwise and that little lug on the bulb is hitting the seat just enough to keep it from seating fully. the holes arms could be worn or something too. you can see a little rust stain next to the lug toward the back of the tank on the flapper.

HomerJSmith

wouldn't the water be dripping from the tank?

No, all the water would be within the tank passage to the bowel.

psb75

"...tank passage to the bowel"?? This is a new one that I wasn't aware of.
This seems kind of...retroactive.

psb75

SO much discussion about proceeding with the easiest, most obvious and least expensive fix for the problem?
Replace--rubber--flapper.

mattmia2

psb75 said:

SO much discussion about proceeding with the easiest, most obvious and least expensive fix for the problem?
Replace--rubber--flapper.

it isn't aligned right. the question is why

ChrisJ

Literally one of the simplest devices on the planet and we've got a 21 comment thread going, soon to go on to page 2.

Change the flapper. The flapper you have is wrong.

Or do the right thing and pull the tank and change all of the rubber and hardware so you know it's not going to fail in a year. There's a good chance you're going to find the tank dripping on the floor in the near future if you don't.

It's very easy to do, just get the right gaskets and tank bolts and be careful not to over tighten the tank bolts.

HomerJSmith

It's a one piece toilet, ain't no stinkin' bolts. See the pics above. At least I think it's one piece as I don't see a triad of bolts. The owner can verify. There are two black circles in the tank but they don't look symmetrical from the flush valve and they don't look brassy.

ChrisJ

HomerJSmith said:

It's a one piece toilet, ain't no stinkin' bolts. See the pics above. At least I think it's one piece as I don't see a triad of bolts. The owner can verify.

What are these I circled in red?

mattmia2

It is leaking right here where the lug is hitting the seat because it isn't centered on the seat. You can see a little rust stain and you can see the mark from the seat is on top of the lug:

HomerJSmith

mattmia2, those appear to be centering guides. Perhaps, it is the wrong flapper after all? Why would one have rust stains? That's the cleanest tank that I have ever seen.

D107

Those are the two bolts, slot tops darkened by age; 2 pc toilet. Will try to get to Home Depot today anfd pick up flapper; if it still leaks then we can go there. Alignment? I'd mentioned that the plumber --probably out of fear of cracking the tank--left the right bolt too loose––9 years ago-- to where the tank slightly rocked. I tightened that but it could still use more. Not sure if that affects alignment.

mattmia2

The rust stain is from the iron in the water that is constantly slowly flowing through that spot. you can see in the first picture that it isn't centered on the seat as well. I'm not sure if that is because the ears aren't in quite the right spot or the arm on the flapper is worn or the chain is a little too tight or the flush arm needs to be bent to be better centered over the seat.

HomerJSmith

OK. 2 piece, good to know. Then one would need to know if the leak is thru the flapper or around the gasket on the flush tube.

Put a little water in the bottom of the bowel even with the top of the drain weir (raise the flapper until no more water runs out of the tank). Add food coloring to the water in the bottom of the tank and let set for 12 hrs. If there is coloring in the bowel suspect that the flush valve gasket that seal the valve to the tank is leaking and not necessarily the flapper.

If the rubber seals on the bolts holding the tank to the bowel failed water would leak on to the flr. Once the tank is removed the flush tube can be tightened to the tank with the large nut on the flush tube if you think it is leaking.
Do the easiest, less time consuming, thing first. Change the flapper.

Larry Weingarten

Hi, I'm agreeing with @mattmia2 and those who say change the flapper. Looking at the first photo, it clearly is not centered. The back of the flapper is just about touching the overflow pipe. I'd look for a Korky brand flapper and see if it has slightly longer arms on it. Take the existing one into the store to compare. Korkys are made with a large flat surface to seal. It could be that simple.

Yours, Larry

D107

Ok, apparently new Korky 2023BP flapper fixed it. I'll keep an eye on it, but almost two hours in, no drop in water level. I snipped out the excess chain links after this photo; despite factory rec of 14 links, it needed 16 and maybe one more. I'll change the other toilet's flapper soon preventively. As I cleaned out the flapper seat, I found much black mold there.

Even though the other scenarios didn't pan out, it was interesting learning about the other possibilities. And a reminder to do maintenance checks at least annually. Thanks all.

HomerJSmith

Ya, you put on a flapper with a rigid plastic arms, good job. It really makes a difference in how the flapper seats.

ChrisJ

Maybe it's just me but, I've had bad luck with 3rd party flappers on my 1.6 toilets. They either don't stay open long enough or they stay open way too long.


I was using the adjustable fluid master ones for years but they would only go 1-2 years before problems with timing.

I ordered the proper OEM flappers for both toilets, a Kohler and a Gerber and both have been perfect for several years now.

After that I'll only use OEM flappers.

D107

@ChrisJ I think for Toto, Korky is considered by some to be near equivalent to OEM. Looking on Supply House for 'toto' flappers, I only see Korky-made listed. The now-failed orange flapper in my post was OEM at the time. It worked for 9 years. The other identical flapper is still in use on another toilet after 15 years. The cause of the other one's demise––being off-center and/or simply being old, could be that the lever was offline, and pulling it towards one side with every flush, made worse by the softer rubber arms. So in order that that doesn't happen again, I'll look closely at the angle and bend the lever accordingly. The rigid plastic arms of the new red flapper may be an improvement.

ChrisJ

D107 said:

@ChrisJ I think for Toto, Korky is considered by some to be near equivalent to OEM. Looking on Supply House for 'toto' flappers, I only see Korky-made listed. The now-failed orange flapper in my post was OEM at the time. It worked for 9 years. The other identical flapper is still in use on another toilet after 15 years. The cause of the other one's demise––being off-center and/or simply being old, could be that the lever was offline, and pulling it towards one side with every flush, made worse by the softer rubber arms. So in order that that doesn't happen again, I'll look closely at the angle and bend the lever accordingly. The rigid plastic arms of the new red flapper may be an improvement.

If it seems to work right go with it.