ᐅ Water on the foundation slab – cause and source of leak unknown
Created on: 21 Mar 2018 10:39
I
ibo85
Hello,
I’m posting here because I’m quite desperate and can’t find a solution to my problem on my own.
Background:
In 2015, I had a house built. I managed the construction myself and hired all the tradespeople directly. Meanwhile, the shell construction company no longer exists — they went bankrupt.
The house has a basement about 2 meters (6.6 feet) below ground level, with approximately 1 meter (3.3 feet) of it above ground.
The slab was poured in one piece. Afterwards, precast wall elements were installed — a “white tank” waterproofing method.
At the time of construction, there was groundwater in the excavation, about 10–20 cm (4–8 inches) high, so still below the slab.
The joints between the precast elements were sealed with bitumen. Metal sheets were installed between the wall and the footing, and in-situ concrete was poured into the precast elements.
About a year after completion, in spring 2016, the interior wall paint peeled off along a horizontal line approximately 20–30 cm (8–12 inches) high and blistered. I hired a company to investigate the problem, but nothing was found. They broke two tiles and checked down to the slab. The slab was slightly damp, but that was all; no cause was found.
Now, nearly two years later, the exact same blisters have appeared on the same wall, and plaster on an exterior wall is wet up to about 1 meter (3.3 feet) high.
I then removed a tile in another spot and broke up the screed down to the slab. There I found about 2 cm (0.8 inches) of standing water. I first removed this water with a wet vacuum cleaner, but this makes no difference, as the water level of about 2 cm (0.8 inches) always returns.
To investigate the cause, I did the following:
1. There is a drainage system around the house with an access chamber that can be opened at ground level. I opened it to check the groundwater level (the drainage is below the slab level) — completely dry, no water at all. However, I have to mention the chamber is located on the opposite side of the house, not where the wall is wet.
Question: Could it be that the groundwater level is higher on the other side of the house? The house is not located on a slope or anything similar.
2. I poured colored dye into the wastewater pipes to see if there is a problem there, then watched the spot in the house where I see the water (the opening). Nothing appeared.
3. I checked the main water meter; it shows only the smallest flow rates, completely still.
4. The basement is heated with underfloor heating. The heating circuit maintains a constant pressure of about 2 bar (29 psi) with no changes.
I’m desperate because I simply can’t be sure where the water is coming from. It is interesting that — no matter how much water I vacuum out — the water level of about 2 cm (0.8 inches) always reestablishes itself. This would suggest groundwater, but the drainage chamber is completely dry, not even damp. No movement on the main water meter, no pressure drop in the heating circuit, no dye found in the wastewater pipes.
Since I just built the house, I’m currently not in a strong financial position. Because the shell contractor went bankrupt, all costs are falling on me.
I would like to hear your ideas and, based on them, start investigating the cause.
At the moment, there is no suspicion that could narrow down the cause, which is why I don’t want to hire a leak detection company. In 2016, they couldn’t find anything either.
I hope you have suggestions or experiences to share on what I could pay attention to in order to find the leak and what is most likely causing it.
Thank you very much in advance for your answers.
Best regards
I’m posting here because I’m quite desperate and can’t find a solution to my problem on my own.
Background:
In 2015, I had a house built. I managed the construction myself and hired all the tradespeople directly. Meanwhile, the shell construction company no longer exists — they went bankrupt.
The house has a basement about 2 meters (6.6 feet) below ground level, with approximately 1 meter (3.3 feet) of it above ground.
The slab was poured in one piece. Afterwards, precast wall elements were installed — a “white tank” waterproofing method.
At the time of construction, there was groundwater in the excavation, about 10–20 cm (4–8 inches) high, so still below the slab.
The joints between the precast elements were sealed with bitumen. Metal sheets were installed between the wall and the footing, and in-situ concrete was poured into the precast elements.
About a year after completion, in spring 2016, the interior wall paint peeled off along a horizontal line approximately 20–30 cm (8–12 inches) high and blistered. I hired a company to investigate the problem, but nothing was found. They broke two tiles and checked down to the slab. The slab was slightly damp, but that was all; no cause was found.
Now, nearly two years later, the exact same blisters have appeared on the same wall, and plaster on an exterior wall is wet up to about 1 meter (3.3 feet) high.
I then removed a tile in another spot and broke up the screed down to the slab. There I found about 2 cm (0.8 inches) of standing water. I first removed this water with a wet vacuum cleaner, but this makes no difference, as the water level of about 2 cm (0.8 inches) always returns.
To investigate the cause, I did the following:
1. There is a drainage system around the house with an access chamber that can be opened at ground level. I opened it to check the groundwater level (the drainage is below the slab level) — completely dry, no water at all. However, I have to mention the chamber is located on the opposite side of the house, not where the wall is wet.
Question: Could it be that the groundwater level is higher on the other side of the house? The house is not located on a slope or anything similar.
2. I poured colored dye into the wastewater pipes to see if there is a problem there, then watched the spot in the house where I see the water (the opening). Nothing appeared.
3. I checked the main water meter; it shows only the smallest flow rates, completely still.
4. The basement is heated with underfloor heating. The heating circuit maintains a constant pressure of about 2 bar (29 psi) with no changes.
I’m desperate because I simply can’t be sure where the water is coming from. It is interesting that — no matter how much water I vacuum out — the water level of about 2 cm (0.8 inches) always reestablishes itself. This would suggest groundwater, but the drainage chamber is completely dry, not even damp. No movement on the main water meter, no pressure drop in the heating circuit, no dye found in the wastewater pipes.
Since I just built the house, I’m currently not in a strong financial position. Because the shell contractor went bankrupt, all costs are falling on me.
I would like to hear your ideas and, based on them, start investigating the cause.
At the moment, there is no suspicion that could narrow down the cause, which is why I don’t want to hire a leak detection company. In 2016, they couldn’t find anything either.
I hope you have suggestions or experiences to share on what I could pay attention to in order to find the leak and what is most likely causing it.
Thank you very much in advance for your answers.
Best regards
miho schrieb:
Yes, that would of course be possible. This reminds me: A few years ago, we had a similar case in a multi-family building where we were renting. After a long search, chemical analyses of the water were conducted to find the cause. Based on contaminants, it’s apparently possible to distinguish the sources. It turned out to be the desalination system. I have a friend to whom I’ve already sent a water sample, but she wasn’t exactly sure what tests to perform to determine whether the water is groundwater, tap water, or wastewater. Which contaminants could be tested for?
miho schrieb:
Such a sudden occurrence is certainly noticeable. Could the tenant have accidentally or unknowingly damaged something during drilling work when moving in? No, definitely not, especially not anywhere near where the pipes run. One reason I want to carry out a sewer inspection is that before the new tenant moved in, I personally did some improvement work, such as applying silicone, acrylic, and expanding foam (also replaced the door frame). During that, I flushed some toilet paper with silicone residue down the toilet, but it was only a small amount. However, to rule this out, I will do the inspection.
miho schrieb:
Has the weather in your area caused a rise in groundwater levels? Or are there any construction activities nearby that are diverting or have recently diverted groundwater flows? Definitely not. February was actually very cold with icy temperatures. There was no significant rainfall. Furthermore, there are no construction sites in the vicinity.
kaho674 schrieb:
Open-pit mining nearby? When they switch the pumps off or on here, the water level of the lake (fed by groundwater) next to it rises and falls by about 2m (6.5 feet). The only thing nearby is a neighbor who has a pond. There is a pump running there repeatedly. I am not familiar with ponds, but I believe it is more likely that water is being circulated within the pond, similar to an aquarium (just an assumption). Given the current cold weather outside, I also think the pump is probably turned off and the pond is frozen.
ibo85 schrieb:
I have an acquaintance to whom I already sent a water sample, but she wasn’t sure how exactly to test it to determine whether it’s groundwater, tap water, or wastewater. What kind of contaminants could be tested for? Unfortunately, I have no idea. I only vaguely remember something from some info sheets from the house management back then. Maybe ask a leak detection company if they know anything about it.
ibo85 schrieb:
No, definitely not, especially not at any point where pipes run. One reason I want to do a sewer inspection is, Go ahead. They can also perform a leak-tightness test on the wastewater pipe without much effort. I recently had this done here because we are in a water protection zone. The process, including a visual inspection with a camera inside the pipe, took about 1.5 hours. The cost was around 250 Euro.
And have them check the drainage while they’re at it.
ibo85 schrieb:
Definitely not. February was rather icy cold. But there wasn’t significant rainfall. Also, there are no construction works in the area.That’s strange. You’re not in a mining or open-pit mining area, are you? Do you know neighbors or farmers with wells who you could ask about their well water levels?
Keep us updated.
ibo85 schrieb:
I have an acquaintance to whom I already sent a water sample, but they didn’t really know how or what to test to determine whether it is groundwater, tap water, or wastewater. What contaminants could be tested for?
Certainly not, especially not anywhere near where pipes run. One reason I want to do a sewer inspection is that before the new tenant moved in, I carried out some repair work myself, such as silicone, acrylic, and expanding foam application (replacing the door frame). During this, I also flushed some toilet paper with silicone, etc. down the toilet, but it was not a large amount. However, to rule this out, I will do the inspection.
Definitely not. February was quite freezing cold. But there were no significant rainfalls.
Furthermore, there are no construction works in the area.Try using Uranin as a dye tracer for the wastewater; it is available on eBay. It is green and UV-active. With a UV flashlight, you should be able to detect any traces.
In the water sample, testing for E. coli is useful, as it is a fecal indicator bacteria. If it is present, it is unlikely to be tap water.
fragg schrieb:
Try using Uranin as a dye for the wastewater; it’s available on eBay. It’s green and UV active. With a UV flashlight, you should be able to detect any residues.That’s exactly what I ordered and tried. Nothing came out of it.
fragg schrieb:
You could test the water sample for E. coli, which is an indicator of fecal contamination. If it’s present, then the water is unlikely to be tap water.Where can this be tested?
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