Unidentified discoloration on flooring near tub and sink

[Neil.Steiner]

My upstairs bathroom has short wall between a tub and a sink, with a door just beyond the edge of the tub. Over the last few months, the floor just outside the door has become increasingly discolored, but I haven't been able to determine the source of the presumed water leak.

I have looked at the valve stems and the diverter inside the wall, and I see no evidence of leaking around them. Likewise for the shower arm, and for everything I can see on the sink side, including peeking back through the pipe holes toward the tub.

At the base of the door frame, there is some wood that is soft to the touch, and it's pretty obvious that something fishy was going on before I bought the place nine years ago, but that still doesn't help me trace the root cause. The discoloration in the picture below between the tile and the marble threshold is new and truly puzzling to me. And I realize that water could be splashing out from the corner of shower, but I have reason to believe that's not what's happening here.

Can anyone suggest what might be causing this, or suggest what I might do to better diagnose the problem? This is the top level of the house, so there is no further plumbing above this.

 

[Dj2]

Could be moisture plus poor ventilation, beside the aging factor.
Things like these are why people remodel every xx number of years.

 

[Sponsor]

 

[Lily Wang]

My upstairs bathroom has short wall between a tub and a sink, with a door just beyond the edge of the tub. Over the last few months, the floor just outside the door has become increasingly discolored, but I haven't been able to determine the source of the presumed water leak.

View attachment 65073​

I have looked at the valve stems and the diverter inside the wall, and I see no evidence of leaking around them. Likewise for the shower arm, and for everything I can see on the sink side, including peeking back through the pipe holes toward the tub.

View attachment 65075 View attachment 65076

At the base of the door frame, there is some wood that is soft to the touch, and it's pretty obvious that something fishy was going on before I bought the place nine years ago, but that still doesn't help me trace the root cause. The discoloration in the picture below between the tile and the marble threshold is new and truly puzzling to me. And I realize that water could be splashing out from the corner of shower, but I have reason to believe that's not what's happening here.

View attachment 65077​

Can anyone suggest what might be causing this, or suggest what I might do to better diagnose the problem? This is the top level of the house, so there is no further plumbing above this.

My daughter's 1 year old bathtub just sprouted a similar problem but I am catching it before it causes too much damage.
I have an Aqualux glass tub/shower door fixed to the wall instead of a shower curtain. Glass edges are siliconed to tile wall and acrylic tub lip.
The bathtub is a Kohler acrylic alcove tub with a built-in flange. The layers are in order from interior to exterior -wall stud, 1/2"ply, 1/2" cement board, redguard waterproofing membrane, mortar, 1/4" thick subway tile finish.
The bathroom floor is oak wood so I could see that discoloration was beginning to happen at the outside corner of the tub on the side of the tub where the plumbing is (shower head, control, spout). That is the wall that gets wettest because water bounces off the body onto the wall. This is also the wall where the shower glass is siliconed to tub and wall (this sheet of glass is fixed, another sheet on hinges is a swing door).

Now over the course of the year, the tub has settled and a horizontal hairline crack has formed between the grout and the tub around the surround of the tub.
The water trickling down to floor has loosened the grout between tub apron and wall tile (rest of the bathroom wall is partially tiled). So there is a small vertical gap between tub apron and tile wall where the grout used to be. In this vertical gap I stuck a fresh piece of folded index card with a bit of felt tipped ink on the paper edge. The purpose of this is to see if water landed on the paper and proof of it in a spread of ink color on the folded card. The other purpose of this is to determine that, indeed, water is leaking BEHIND the finish wall tile, not in front.
So clearly, water is migrating behind the wall tile, probably between the built-in flange and cement board. While this water is contained everywhere else in the tub where there is a flange , at the outside edges, the flange ends and the water has nowhere to go but drip over the edge of the tub assembly.

Fix attempt 1) dig out the grout at the meeting point between glass, tub and tile about .75" into bathtub side of glass divider. Shot silicone in there. Less water drip but still water is dripping.

Fix attempt 2) dig out a larger "weep hole" in the corner, all the way down to the cement board (this would mean a 3/8" deep gap, again on the wet side of the glass enclosure. Siliconed a "drip cap" over the weep hole and continued the silicone to tub edge. Theory here is that the silicone will lead the water via capillary action AWAY from the wall and drip into the tub. I got more water leakage on the outside of the tub with this effort.

Investigated the hairline crack and determined after slipping thin newsprint in there that there's A LOT of water trapped by capillary action between flange and cement board. If you think about it, the cement board is not attached to the tub in any waterproofed way. There are tiny gaps all along the assembly behind the tile finish.

Fix attempt 3) Gonna try this tomorrow cuz she just took a shower and I want the entire assembly to dry out before it do this. I am going to caulk the horizontal hairline crack plumbing wall with DAP siliconized caulk.

 

[Lily Wang]

Ugh, sorry about the divided reply - hit the wrong button.

Fix attempt 3 cont.) Only siliconing the crack on the plumbing wall; will leave the hairline cracks on the other walls because those walls don't get so much water splash. Water that migrates behind the walls still needs a way to escape.

If this doesn't work my daughter's just going to have to keep a sponge in the trouble corner.
Here are some pics of the bathtub. The soaked newspaper slipped in the horizontal hairline crack shows me how much water is trapped back there.