Moisture Reading Between Boards

[KevinC76]

Hi everyone,

Thanks to all who contribute--I learned a lot (especially about turning a main line back on!), even if I didn't find a precise answer to the question I had:

Do elevated pin-type moisture meter readings between wood floorboards indicate a leaking toilet?

A few weeks ago, the wood floor in our downstairs bathroom seemed "off," and so I bought a moisture meter and found several spots in the wood were reading high. The best guess was that a new washing machine, which drained into the sewer line at the same spot as the toilet, had caused a sort of backsplash. The toilet had begun gurgling loudly and the bowl level went down a couple of inches each time the washer ran. The plumber moved the drain line so it hit about ten feet away, which stopped the gurgling. He also removed the toilet, saw no visible damage anywhere, and replaced it (with a new wax ring and supply line).

However, two weeks later, although the toilet isn't gurgling and the wood is reading all right (between 7-11 on a pinless meter, and no high single spots when checked with a pin, either), there are much higher readings between the boards, ranging from 15-22, on both sides of the toilet along either side of the board where the bolt secures the toilet to the flange. (This is with the pins inserted between the boards; if I place the pinless meter over a seam, the reading is about the same as above the board.)

We stopped using the toilet, and have had a fan going for a few days, but the numbers haven't gone down. If anything, they've gone up slightly. Do measurements (taken with a pin meter) between the boards indicate an ongoing problem?

I'm grateful for anyone's next suggested steps.

 

[Jadnashua]

Is the wood installed over a subfloor or a concrete slab?

 

[Sponsor]

 

[KevinC76]

Is the wood installed over a subfloor or a concrete slab?

 

[KevinC76]

Whoops--sorry.
It's over a subfloor. I haven't detected any moisture down there, either, but unfortunately due to a previous incident a few years ago, the subfloor directly under the toilet isn't entirely accessible: a sub-subfloor was installed to support the toilet. That's reading fine, as is the original subfloor around the toilet.

EDITED TO ADD: I should add that the level in the bowl goes down slowly over time, but it seems to me that it coincides with the draining of the washing machine. It no longer gurgles, but the water in the bowl has gentle waves while the washer drains and ends up lower as best I can tell--about an inch over two days or five loads of laundry. I know that's probably not a good thing but it's better than the gurgling and two inch drops on one load. . . .

 

[Jadnashua]

If I had to guess, and this is a guess without more info, it appears that the washing machine does not have a proper vent and the pumped water moving through the line is suctioning some water out of the toilet bowl.

The only other reason I can think of that a toilet bowl would drop the level is if it is leaking through a crack that has developed. Well, it could rock the level a bit if it was really windy and the vent pipe through the roof was getting pressurized. A toilet bowl is sort of like a teapot...tip it, or shake it, and some of the liquid could come out. That outlet in a toilet is called a weir.

 

[KevinC76]

Thanks for the ideas! I had thought about the vent, but not about the wind. I just can't see how water leaks out from either of those. The crack is probably most likely; putting your two thoughts together, though, makes me wonder whether the water is pushed or pulled through the crack more noticeably if the washing machine causes the suction.

For whatever it's worth, it's a 1.6 gpf toilet. I was sort of dismissive about "Oh, it's only a little bit of water leaking out," but it's probably close to two cups for every inch that the level decreases. If the water is leaking out, that's a lot and would explain the moisture between the boards.

 

[Jadnashua]

Unless there's a faulty wax seal, or the flange is cracked, or the toilet itself is leaking, anything that goes down the drain should not be causing a leak into the subflooring.

 

[KevinC76]

That's my thought, too--which is why I'm trying to figure out if moisture readings between the boards indicate a leak of some sort. I'd rather not take out the toilet or rip up the floorboards to check unless I need to!

 

[KevinC76]

I had a plumber come out, and he took out the toilet. Definitely elevated readings in the floorboards right near the toilet. His guess is that it is moisture more than water seeping out when the washing machine pulls it out of the toilet.

So he (a) replaced the old flange that was corroded, bent, and cracked and (b) used a rubber ring instead of a wax ring to keep any moisture in the system. I'm doubtful that could account for the readings I saw (18-24) but I'll give it a shot. I've got fans above and below the flooring to try and speed up the drying.

 

[KevinC76]

The level in the toilet is still dropping, especially overnight (about 1/4 inch), but the moisture readings have ticked down a bit, definitely not going up. I wonder if it does have to do with the vent if the level goes down more overnight. It's been windy here in Virginia.

But as long as it's not leaking outwards, I can live with this. Thanks for the help!

 

[Reach4]

he level in the toilet is still dropping, especially overnight (about 1/4 inch), but the moisture readings have ticked down a bit, definitely not going up. I wonder if it does have to do with the vent if the level goes down more overnight. It's been windy here in Virginia.

Possible.
1. close the lid at night to keep the dog out.
2. Put tissue on the floor near the toilet base as a tattletale for bad aims.

 

[KevinC76]

1) No dog. We do have another baby on the way--which is probably why I'm so worried about this--but it'll be a while before he'll be able to drink from the toilet.
2) The boys have been told either to sit or to use the upstairs bathrooms, but because we have fans in there to dry out the wood, no one's used it.

I just find it odd that right before bed, about ten hours after it was last flushed, the level looked about the same as it had been, maybe a tiny, tiny bit lower (and that was with showers, laundry, etc.). I checked it this morning, only eight hours later and not much plumbing usage, and it had clearly dropped a quarter inch.

 

[Reach4]

A tiny crack is possible, but that would not act on the schedule you observe. How about unscrewing the AAV in that bathroom? Even better would be a blind test where the AAV was removed or not based on a coin flip. You take your measurement, and then find if the AAV had been off overnight. Of course the smell could give it away.

The following are some thoughts on your test protocol. They are not based on experience.

Maybe rig a depth gauge with a finger that goes down to almost the full water surface level. It might be easier to judge a change from 1/4 inch gap to 1/2 inch gap than to look at a mark on the bowl.

While testing, consider closing the valve at the wall. What if you had a leak that was partially hidden by water leaking past the flapper. Seems unlikely to be the case, but while you are in a testing mode, its an easy test to add.

Another test would be to add some dish detergent to the water. The thought would be that wicking action would be modified.

 

[KevinC76]

That's a really helpful list of suggestions--thank you! With the new baby arriving any day, I may hold off on the AAV test temporarily, but I'll try the other things out. I don't think the water leaks down from the flapper, as the level can go down pretty significantly over the course of four or five days, but it's worth checking.

The other thing I wonder about is whether the fans we have to dry out the moisture--two above, two below--could be affecting the levels. Again, that probably wouldn't account for the drop occurring overnight, except I just remembered that the ones under the house turn off overnight, so there's just the fans from above.

I did check the level, and the toilet is tilted ever so slightly forward (toward the bowl).

 

[Reach4]

Also, watch the level in the problem toilet while somebody flushes the other toilets. Look for ripples or other disturbance.

 

[KevinC76]

Well, bathroom usage is frequent enough with five of us in the house. That doesn't seem to have a noticeable effect though.

 

[Jadnashua]

If you want to see if it's evaporation, put a pan or glass with some water in the same area and compare levels. In VA this time of year, the humidity levels tend to be fairly high, but with a/c running, it could be moderately dry...easy to tell with a simple test.

 

[KevinC76]

That's actually a very good idea. It's definitely humid outside, although the house still has most of its winter dryness. The heat has even kicked on more than the A/C of late. I've had the bathroom door closed with the fans running inside and it definitely FEELS dry when I go in.

For whatever it's worth, the levels dropped noticeably during the day today, so maybe it's not a nighttime thing. (I noticed this before I made a measuring tool.) But we did do four loads of laundry, so it could be the washer pulling water out.

 

[KevinC76]

Well, I haven't taken a science class in twenty years and it showed.

I forgot to measure the water level, although it's lower. Almost a quarter cup of water evaporated from the pan, except that it doesn't make for a good comparison because I left the toilet lid closed, whereas the pan was open.

In any case, the moisture readings between the boards bounced back up, from about 18.5 when the toilet was water-free Wednesday morning to 23.0 this morning, so it really does seem like a leak somewhere and not just evaporation or some sort of wicking/siphoning issue.

Back to the drawing board.

 

[Plumbs]

Get some dye and put it in the toilet and down the washer drain. You need good quality dye for this, not food coloring or those little tablets they sell for toilets.
I've had good results with this: https://www.homedepot.com/p/Eco-Clean-1-Gal-Green-Water-Tracing-Dye-GREENDYE-1/305766181