Case of the hissing Toto Ultimate and dropping tank water level

[not_handy2]

Toto ultimate toilet (approx 12-15 years old)

I installed a bidet seat to the toto ultimate and noticed the water supply connection to the fill valve was leaking despite tightening. I replaced the original fill valve with the korky 528T. Over a period of months I've been dealing with persistent hissing from the fill valve first appears weeks after the 528T installation. Over a period of 2-3 months, I have replaced the parts below with the hissing to return again teased with occasional silence. Sometimes the hissing is bad. Water level in tank dropping.
Replaced in total:

• installed new 528T fill valve
• replaced flapper
• replaced flapper with korky premium flapper
• adjusted the chain many times
• replaced fill cap
• disassembled multiple times the fill valve, cap and filter

I was going to replace the flapper and fill valve but I decided to investigate the water level dropping whether water supply on or off. When water off, there is no sound of a leaking flapper. The water loss is silent. I tried tightening the drain/flash valve screws today but water level still dropped. See picture showing the water level change in a 12 hour period (top pencil mark to water level).

Before I throw more money at the toilet...thoughts? Is it hammer time on the toilet?
Signed, very frustrated

 

[Reach4]

I was going to replace the flapper and fill valve but I decided to investigate the water level dropping whether water supply on or off. When water off, there is no sound of a leaking flapper.

Is your symptom just sound, or does the water level drop?

I was going to replace the flapper and fill valve but I decided to investigate the water level dropping whether water supply on or off. When water off, there is no sound of a leaking flapper. The water loss is silent.

Does that mean that the water level stayed up with the stop valve at the wall closed? If the water level drops with the stop valve closed, how far does it drop?

So what happens, besides silence, when the tank is full and you close the stop valve?

How high does the water fill the tank after a flush, and how far does the water drop before the noises start? Or is there always noise when the stop valve is open?

 

[Sponsor]

 

[not_handy2]

After a flush, the tank water rises to about 1/8 to 1/4 inch below the over-fill tube. I have noticed the tank level dropping over time. At times, the fill valve is hissing and other times not at all. It maybe timing when I walk in to listen and check. That part part is stumping me. I definitely notice the water level gets lower compared to the original water level stains before the fill valve leaked.

I think the water level drops more so when the water supply s off. I haven't checked the fill valve float position when it's hissing. Didn't think about that until now. I could see how low the level drops over 2-3 days with the water supply off.

With water supply turned off after filling, the water level drops about an inch over a period of hours (12 hours in the picture). l thought maybe the hissing fill valve is reacting to the drop in the tank water level (??).

 

[Reach4]

With water supply turned off after filling, the water level drops about an inch over a period of hours (12 hours in the picture). l thought maybe the hissing fill valve is reacting to the drop in the tank water level (??).

That refill, with hissing, would be normal reaction to the slow drop in water level if the water supply turned on. The hissing then is not a problem with the fill valve, but just making up water that has been lost.

So if the water is on, and you don't use the toilet, you hear the hissing maybe every 6 hours for a few seconds?

Recapping symptoms, with the water off, the level drops at least an inch, or to about 1-3/16 below the overflow. That most likely would be caused by something at the bottom, such as the flapper. But it is not impossible to have a crack in the overflow tube. That is rare.

If you could let the water keep dropping, you could see if the dropping stops at the level of the flapper, or goes lower. You could lower the water to maybe 1/2 inch above the flapper/flapper-seat level and see if the dropping stops at the flapper edge, or continues lower.

Also, with the water level way down, and the water not sloshing, you could drop a drop or two of food coloring into the water near the flapper. Watch for the coloring to show the path of the flow.

A flush valve flapper is part of a seal. The flapper seat is the mating part. You could feel that seat for any imperfections.

 

[not_handy2]

I let the tank sit for another 24 hours to see how much further the level would drop. It looks like it is stabilized with no change since this morning. See pictures to where the tank level is currently at. I can see why the fill valve would hiss based on the level. However, I still don't have an answer to why the water level dropped. It doesn't look like it is flapper issue or a leak in the drain valve gasket????? I am stumped. Could there be a leak at the top of the overfill tube but I don't see any crack?

 

[Reach4]

It looks to me as if your overflow tube has an extension, and there is a leak at where the extension meets the regular part of the overflow tube.

Was that your DIY addition to try to get a stronger flush by supporting a higher water level? Or was that done by the previous owner?

Anyway, if you want to keep that extra height, maybe some kind of waterproof stretchy tape would seal that gap. I am thinking of self-fusing silicone tape, but there could be other things. Maybe some kind of sealant could close the gap.

Or maybe get a piece of rubber hose that goes over the outside up to the level of the top of your extension. A worm gear hose clamp could secure the hose to the regular overflow tube... but not to tight, so as to not crush the tube.

Or maybe a piece of shrink tubing, but don't damage the plastics as you heat.

Or maybe just adjust the fill level lower.

 

[not_handy2]

Interesting!!!. I bought 2 new Toto ultimate toilets from a local Toto dealer many years ago . The other Toto ultimate has the same extension. I remember the business owner saying he would make both toilets a 'GMax' but he didn't tell me what he did. I'll look at the extension more closely and explore finding a sealant or epoxy. I see Toto no longer makes the original drain valve but has another a replacement drain valve (THU460.15E-A). Will let the group know if solution found. Probably the easiest is to adjust the fill valve.

 

[not_handy2]

Just a follow-up. I decided to do a quick fix that should last awhile. I applied marine epoxy to the joint on Friday. The toilet has been silent for 3 days straight, no hissing and no drop in water level in the tank. Thank you Reach4 for pointing out how to find the leak as well as identifying the extension. I thought that the overfill tube was oem one piece until you pointed that out. Silence is great.

 

[Plumbstar]

The Toto flapper has always been an issue as most 3" flappers are. Fortunately, Toto has an easy & inexpensive fix to upgrade the flush to the latest design. I rarely replace the flappers anymore. Just order the appropriate flush tower and you good to go. Toto website will give you the appropriate replacement model number. You can easily upgrade a Toto Ultimate to an Ultramax by installing the Ultramax flush tower into the Ultimate. The basic china toilet is the same. New flush towers are about $30 but will last far longer than just replacing the flapper