Korky fill valve hissing after cap replacement

[TJG]

Hi all,

I had a problem with my Toto Aquia where water was leaking into the bowl. I read other related threads in this forum and figured it was worth replacing the cap on the fill valve (water stopped leaking into the bowl when I shut the water off). Bought the Korky replacement cap, installed it, and now the fill valve is hissing and continues to slowly fill the tank even after the tank is refilled. I also noticed that when it's filling, some water seems to be pouring out from underneath the cap, and I assume it should all be going through the tube to the flush valve. Seems like I'm not getting a tight seal with the new cap... though I also tried putting the old cap back on and it now also has the same issue.

I also tried cleaning out the whole fill valve as shown in this video:

Would the next step be to replace the entire fill valve now? Or could it be something else?

 

[Jadnashua]

Are you sure you've fully seated the cap on the top of the valve assembly? You should feel a slight click as it reaches the stop, if I remember (it's been a bit since I needed to replace one). Hold the body of the valve while installing the cap.

Keep in mind that the water to refill the tank AND the bowl, both come out of that seal, so some will be going down into the tank and the rest directed out the hose for the bowl. As long as it stops once full, that part is not an issue.

 

[Sponsor]

 

[TJG]

Are you sure you've fully seated the cap on the top of the valve assembly? You should feel a slight click as it reaches the stop, if I remember (it's been a bit since I needed to replace one). Hold the body of the valve while installing the cap.

Yes, quite sure it's seated properly.

Keep in mind that the water to refill the tank AND the bowl, both come out of that seal, so some will be going down into the tank and the rest directed out the hose for the bowl. As long as it stops once full, that part is not an issue.

That's good to know, wasn't sure if that was related to the issue.

 

[Jadnashua]

You could slightly close the shutoff at the wall. You might also want to check your water pressure. If it's over 80psi, at least in the USA, you'd be required to install a pressure reduction valve. High water pressure will decrease the life of any of the seals in things of the home, and also cause noises that lower pressure doesn't. Things are designed for >=80psi.

 

[TJG]

You could slightly close the shutoff at the wall. You might also want to check your water pressure. If it's over 80psi, at least in the USA, you'd be required to install a pressure reduction valve.

I gave that a shot, but leaving the shutoff half open didn't make a difference.

To be honest I don't know how long this issue may have existed, as the hissing isn't noticeable once the lid is on the tank. For all I know it may have been going on since the toilet was installed 7yrs ago. Given that, I'm thinking that perhaps replacing the whole valve is the way to go. I assume the Korky QuietFill Platinum is the way to go?

 

[Reach4]

Given that, I'm thinking that perhaps replacing the whole valve is the way to go. I assume the Korky QuietFill Platinum is the way to go?

After you check the water pressure.

You can get a garden hose-connection (GHT, GH) pressure gauge for under $20, and maybe significantly less.

You can connect to a laundry tap, outside, or to the water heater drain.

 

[Jadnashua]

If you can hardly hear it with the lid on, I'd just leave well enough alone. As long as it now works reliably otherwise.

You need a fill valve that has either adjustable bowl/tank fill or one specifically designed for your toilet, otherwise, you'll either waste water with each flush, or have inadequate performance. Both the tank and the bowl should be filled at the same time. If either is short of water, things don't work well, and overfilling just wastes water. Those made for Toto (with the Toto logo) have a restrictor to ensure the proper tank/bowl proportions.

 

[TJG]

It took me awhile to get around to it, but I finally measured the water pressure and was pretty surprised to see it at 90psi. I just assumed that being a dense residential area of a big city, it'd be a lot lower. In any case, looks like we'll have to have a PRV put in before I bother doing anything further with the toilet. Thanks for the advice!

 

[Reach4]

One more test for you: dribble water from a faucet, and see if you still have ~90 psi. It is possible that the incoming water could be 60 psi, but the pressure rose during your test due to thermal expansion. If the pressure is below 80 while dribbling, you may only need to add a suitably-sized thermal expansion tank.

With a PRV, you will also want a thermal expansion tank added if you don't already have one.

If that 90 psi was not while your toilet was hissing, the water pressure may be getting significantly higher at times.

 

[TJG]

One more test for you: dribble water from a faucet, and see if you still have ~90 psi. It is possible that the incoming water could be 60 psi, but the pressure rose during your test due to thermal expansion. If the pressure is below 80 while dribbling, you may only need to add a suitably-sized thermal expansion tank.

Perhaps a stupid question, but if I've tested on a cold water line, how would that be affected by thermal expansion?

 

[Reach4]

Perhaps a stupid question, but if I've tested on a cold water line, how would that be affected by thermal expansion?

The pressure on the hot and cold lines will be the same if water is not flowing much. As the water in the WH expands, if the water cannot be pushed back toward the water main, the pressure will rise equally in hot and cold lines.

 

[TJG]

The pressure on the hot and cold lines will be the same if water is not flowing much. As the water in the WH expands, if the water cannot be pushed back toward the water main, the pressure will rise equally in hot and cold lines.

Ah I see. Could that still happen with a tankless water heater?

 

[Reach4]

Ah I see. Could that still happen with a tankless water heater?

Equalization of hot and cold pressures? Yes.
Does a tankless WH need a thermal expansion tank? I don't know. I see different opinions.

 

[Jadnashua]

Many places either have, or are installing check valves to their water customer's equipment. This is to prevent the possibility of contaminants being pushed back into their supply system and potentially impacting many customers. As a result, this creates what is called a closed system. A PRV added would also create a closed system. Some tankless systems actually have a small tank in them used for when you hook up recycling. But, while a tankless might not necessitate an expansion tank always, if you otherwise have a closed system, you'd need one regardless of how you heat the water.

One really enlightening thing might be to leave that gauge in place, assuming you bought one with a second, tattle tale hand, and see where it peaks over a typical 24-hour period. What you might see during the day, may be low compared to the late night when little water is being used, and the utility is pumping water up into storage tanks (water towers) to provide the volume needed during the day.

Keep in mind that just gravity will increase, decrease the water pressure based on the elevation of the supply and exit point...that variation is about 0.43 pound/foot of elevation change. So, say you were checking in the basement, and then could check it on the second level, there might be a 10' difference in elevation, the water pressure would be lower by 4.3#, just because of the elevation change. That's why water towers are tall and narrow, rather than low and wide.