Thank you
@Duder for your recent post, and previous posts by
@Henry Rollins and
@Terry; these helped us figure out a problem we were having. We were about to call a plumber out, which was especially unappealing due to the pandemic. Posting this to potentially help others that may come across this discussion later.
Short version: we were getting water hammers sometimes with our Toto Drake II from 2019. Solved by fully opening water intake valve.
Longer version:
We remodeled our upstairs hallway bathroom in 2019 (finished around August 2019) and selected a Toto Drake II as our new toilet. Contractor and their plumber subcontractor installed it and there was no problems for 11 months. Then only July 4, 2020 in the evening, we had our first water hammer event. Scared the dickens out of some of us; we had never even heard of a water hammer. For this first one, we had flushed 3-4 times without waiting for the tank to finish filling, which is something we rarely do. After that, we would sometimes have water hammer instances even with a single simple flush. This mostly happened after 10pm at night or later, not during the day. (Maybe the city's water pressure is higher at that time due to fewer water users - not sure.)
Coming across this discussion, we checked what kind of fill valve we had in our toilet. It was the same green one as
@Henry Rollins posted a picture of in 2015 -- the one people here are saying shuts off too soon. We also have the same one for our new Toto Drake II for our downstairs bathroom; that one was installed this summer and never had a water hammer.
The water hammers have gone away now for two weeks, so I'm tentatively declaring the problem solved. Up until the night I solved it, I had assumed that the water intake valve was fully open -- that the plumber would have put it in that state after completing the toilet install. However, by accident I discovered that that was not the case; it has been only halfway open (halfway through the full range of rotation). After opening it fully we have had no water hammering.
The tank refilling sound is notably different now too.
I still don't fully understand the mechanics of what was happening or why it happened with one flush but not another (and some of it it seems counter-intuitive), but I'm getting the idea was that the fill valve was sometimes needing water to come in at a faster rate that it actually was, with the half open water intake valve. When it didn't get that, this undesirable circumstance arises.
Main takeaway: if you are having water hammers happen, check your water intake valve on the wall to make sure it is fully open (fully rotated counterclockwise).
-- Jim