View Full Version : Toto - Leaky GMAX fill valve

07-04-2007, 11:18 AM
We installed three new Ultramax toilets in February 2007. The fill valves on all three leak (sometimes a constant drip, sometimes a sporadic spurt). I have cleaned out the filter (it was spotless) and replaced one of the valves completely with a new one and it leaks also. When they leak, the water comes out of the fill tube between flushes. After a flush when the tank is filling, water usually leaks out of the valve cap before the fill tube.

Any suggestions? Thanks.


07-05-2007, 08:37 AM
Water can leak from the cap area duing a refill, that's part of the antisiphon, that's normal.

Water from the tube, that points into the overflow tube, that would be normal. That fills the bowl after a flush.

If, after everyything has filled, then things should go quiet.

There are two fill valves used on the Ultramax.

The Korky type, can be cleaned or repaired using these instructions

If you have the type, with the screw adjustment, and it does not come to a complete shutoff when finished, then you would be looking at replacement.

Looking inside the Ultimate tank, wth the Korky style fill valve.

And with the fill valve that has a screen at the bottom where the water comes in.

03-15-2009, 12:14 PM
I have an ultramax with the valve pictured in the lower picture. Can anyone tell me (a) what the model number of that valve is so I can google it, and (b) what the white screw is for?

I'm getting a pretty steady drip from the little black hose. The flapper is seated tightly, but water just drips into the fill tube.

Not sure if that screw would allow me to adjust anything.

03-15-2009, 12:34 PM
The white screw allows you to adjust the height of the float so you can raise or lower the water in the tank.
If you have a Ultramax with the G-max the new fill valve is part #TSU18A.

03-15-2009, 03:41 PM
You may want to invest in an inexpensive water pressure gauge (costs about $10 at a big box store). Toilet fill valves are more sensitive to excessive pressure than many others in your house, and if all three are leaking so soon, you may need a pressure reduction valve to protect the whole house. Get one with a max reading tattle tale and leave it attached overnight. It shouldn't exceed 80#, and if it does, you've found the reason things are leaking.

11-11-2009, 05:36 AM
Can you replace the TSU18A valve (bottom picture) with the version on top (Korky 528Z)? The top version seems to be more readily available and repairable.

10-06-2012, 06:24 AM
This is an excellent website with good information. Others have asked for the instruction manual for TSU18A (lower photo), but Terry provided a link for an instruction manual to the one in the upper photo. I then wasted a lot of time searching the web for the manual to the TSU18A in the lower photo ... before I realized that it is a "non-repairable" fill valve! Is this correct? If this is correct, then I would suggest changing the caption to BIG BOLD lettering.

10-06-2012, 10:04 AM
There is actually a pretty good little sheet from Toto on how to service both types of valves. Here is is: Toto Valve Serviciing (http://www.bay*******************/images/documents/voretolavallefillvalveinstructions-rev06-1.pdf)

The Voreto valve (the one on the bottom, made in China from a Toto design) comes in a lot of subtypes with different TSU numbers, but does have some commonalities. Generally, you can clean its filter, but you can't replace the working parts just by swapping a little cap, like you can with the Korky.

Personally, I dislike the Voreto valves and so have tossed mine and replaced it with the relevant Korky (upper photo) model (which brand is now the Universal replacement valve for Toto products). You can get one of those at Lowe's, part number 528MPK (528MP at other retailers).

10-06-2012, 10:05 AM

With this valve, drop the water supply, and using a needle nose pliers, pull the filter screen from the inlet, clean, and then reconnect the supply line.


The screen in the inlet. A needle nose pliers will remove it for cleaning.

10-10-2012, 06:42 PM
Terry, Thank you for the reply.
Unfortunately the problem is not with the water inlet screen.

For the replacement, should I use the suggested 528MPK model?
Home Depot only carries the white top 528 model.


10-10-2012, 07:28 PM
I just found on this website the answer to my question on 528 vs. 528T vs. 528 MPK.
I would also like to thank wjcandee for the link to TOTO Valve Servicing.