Bathroom leak mystery

[HouFix]

Hello. I live in 1400 sq ft townhouse with a downstairs powder room. There's a leak but plumber can't figure out where leak orginates.
Here's what I know:
1. The leak only happens when the water shutoff valves are off.
2. Running water through the sink doesn't cause water leak or condensation on the pipes or valves themselves.
3. I filled the vanity with water and left it. Then let the floor dry. Draining the sink didn't cause any water damage.
4. The bathroom was recently renovated so this is a new vanity, pipes under sink
5. The water accumulates right in front of the vanity and can be seen only by pressing down on engineered floor planks. The water has never raised
above the floor planks - maybe because i turn the valves off.
6. There are no signs of water on the vanity wall or the flooring behind the vanity in the dining room.
7. Nothing else appears to be wet except the little puddle underneath the floor tiles when you squish them.

Thanks for any ideas 🙂

 

[WC1]

Im sure you have considered this but point Number 1 suggests very strongly that one of the shutoffs is leaking in the off position.

 

[HouFixReply]

Im sure you have considered this but point Number 1 suggests very strongly that one of the shutoffs is leaking in the off position.

Thanks for your response. I didn't think of this because, for sure, it doesn't leak when the valves are shut off. I can tell because there's no water buildup or squishy noise underneath the floor planks. When the valves are on, then the water build up happens, but there is no sign of water anywhere except under the floor planks.

 

[WC1]

1. The leak only happens when the water shutoff valves are off.

 

[Ric2013]

Very hard to help someone when they contradict themselves.

OP: please check what you've written next time and use the edit button or issue a correction otherwise it makes any attempt to help counter-productive for all parties.

 

[Aquarius]

Wind up post? Given the date, and now user seems deleted?

 

[Ric2013]

I don't think so. In any case, the OP returned yesterday (above) but seems to have lost original login.

 

[HouFix]

Hello. I live in 1400 sq ft townhouse with a downstairs powder room. There's a leak but plumber can't figure out where leak orginates.
Here's what I know:
1. The Does Not happen when the water shutoff valves are off.
2. Running water through the sink doesn't cause water leak or condensation on the pipes or valves themselves.
3. I filled the vanity with water and left it. Then let the floor dry. Draining the sink didn't cause any water damage.
4. The bathroom was recently renovated so this is a new vanity, pipes under sink
5. The water accumulates right in front of the vanity and can be seen only by pressing down on engineered floor planks. The water has never raised above the floor planks - maybe because i turn the valves off.
6. There are no signs of water on the vanity wall or the flooring behind the vanity in the dining room.
7. Nothing else appears to be wet except the little puddle underneath the floor tiles when you squish them.

Thanks for any ideas 🙂

1. The Leak Does Not Happen when the water shutoff valves are off.

 

[HouFix]

1. The Leak Does Not Happen when the water shutoff valves are off.

To the person who posted earlier and said I contradicted myself, thank you for pointing it out, the folks here are very helpful, what a great resource. Unfortunately, I was overwhelmed when I first posted this but reading through these posts has been educational.

 

[WC1]

Per point no. 4
When was the bathroom recently renovated?

 

[HouFix]

Per point no. 4
When was the bathroom recently renovated?

Last year this time. I paid someone to come in a demo it. Then the engineering flooring was installed on the first floor. Then the toilet and vanity were installed.

 

[HouFix]

picture

 

[HouFix]

the water accumulates in 1 spot. assuming water would eventually be everywhere if i didn't turn the valves off.

 

[WC1]

If I were looking for that leak I would first take a price if tissue paper and press it all over each feature of the accessible pipework as shown, especially at the back of the feature, each time inspecting it carefully under good light for signs of moisture. If possible do several times over 24 hours.
If the puddle appears but the pipework is dry it can be ruled out.
After that I would consider removing some sheet rock and inspecting the pipework behind.
The shutoffs may be a red herring.
A periodic fluctuation in water supply pressure may be causing the leak.
Perhaps when the work was done, a joint within the wall was disturbed.
Something is amiss with the plumber being unable to find the leak. Either he doesn't want to find it or he's not a real plumber.
Did he do the renovation?

 

[ShaunCorbs]

Is the bowl loose eg sink ?

 

[Ric2013]

I'm thinking water may be getting between the floorboards and running down the tongue and groove by capilliary action. I'd check along that line of the flooring.

My original thought was a spray from below, but if no evidence of leakage in the room below, this seems unlikely (unless the floor separator has a highly water resistant barrier such as 4" of concrete which could hide the leakage for a long time).

 

[HouFix]

Great advice. I'm excited to try the toilet paper. I'm even thinking to use a pipe cleaner around the toilet paper to secure each section. Very much appreciated!