[diyguy1]

This crusty spot on my basement concrete floor keeps returning after I scrape it off.

I'm wondering what's causing it, and the best way to permanently patch it. It's under my washer/dryer, in an area that usually remains dry.

Photos are before and after scraping it off.

Thanks.

 

[Nealtw]

https://www.nachi.org/efflorescence.htm

 

[Bud9051]

Neal's link on efflorescence is probably correct and if so indicated moisture is evaporating through that spot and leaving the minerals behind. But the problem may be bigger than that crust you see.

i see a hose to a floor drain that may be increasing the amount of water under that slab. I would suggest that be discharges into the sewer drain or pumped outside. But unknown is what other water issues there might be, do you have a sump pit?

Resolve the moisture under the concrete and then repair that spot. Also notes is that the floor appears to be painted or otherwise partially sealed making that spot the easiest point of exit. Sealing everything may just push the moisture out somewhere else.

Bud

 

[diyguy1]

Thanks Bud, The hose you see is just the overflow for a softener, so it’s never carried any water.

But the main sewer line is under this area and until a couple of years ago had a crack (discovered during a video inspection) which was repaired back then. No sump pit, but I suspect there’s some moisture below the slab on this side of the basement, but not a lot. It takes months for that crust to build up.

 

[Bud9051]

There are basic moisture prevention steps, may already been solved, but directing downspouts away from house, flower beds ext to foundation, landscaping to slope runoff away from house are a few.

IMO, all basements should have two sump pits, one for below the slab sealed against radon and a second one open to above the slab to handle broken water pipes. I've seen both types of basement flooding and with no place for water to go it becomes a pond. If you have finished your basement be sure to check if it is included in your insurance including water damage.

Not a pro on the issue, but as nasty as that crust looks I wonder if the source is other than mineral deposits, thinking sewer related. The efflorescence I've seen is usually a white mineral deposit.

Research your region for radon but start with a hole in the slab somewhere to see if it fills up with water. More research to determine where.

Bud