How to fix high water table under house

Hi please help! We bought a house on a hill in NJ last winter. There are houses on our upper slope and also houses down slope.

Table of Contents Show

What Is a High Water Table?
Different Types of Water Tables
How Can a High Water Table Affect My Home?
How Do You Measure the Water Table on Your Property?
What Can You Do About a High Water Table?
How do I reduce the water table in my house?
How long does it take for a water table to go down?
How can a water table become raised or lowered?

During the really wet season this summer, our basement got damp, a small section even got water, like 1/8 inch deep. So we installed an interior french drain and a sump pump. After that, it's dry again, but only that the pump keeps pumping water out every 10-20 minutes.

During the Hurricane Sandy, we lost power for 12 days. This gave us a chance of stopping the sump. We saw that after 2 days, the water level in that pit was stabilized at around 10 inches below the slab surface and it has been at around that level during the last few days - maybe one inch lower but definitely not much - the pump was still submerged under the water.

Is this where the water table level is? I don't understand how come a house on a hill can still have high water table: why the water doesn't go to our neighbors property, there are plenty of them down slope..

And how do I fix this problem? If we need to dig an exterior french drain, we will have to dig really really deep - like 8 feet.

Any advice will be much appreciated!

High Water Table Solution

In order to discuss a high water table solution we must first define what exactly a water table is. Basically, a water table is the underground depth where the ground is totally saturated with water. There are a number of factors that contribute to the formation of the water table. The weather is a factor because every time it rains water seeps down into the water table. Snow can also affect the water table because every time that snow melts the water that it forms also seeps down into the water table.

Homeowners need to be concerned about a high water table primarily because it can lead to a leaky basement. At DrainCom we have been dealing with leaky basements for many years. When dealing with a leaky basement what we usually find under the basement concrete slab varies tremendously from finding completely dry soil to finding so much water that it looks like a small river.

Normally there is no need for concern for homeowners in Toronto and the GTA because the water table in these areas is at a much lower level than the depth of the basements. However, with the type of weather that we have been having the last couple of years like heavy pouring rains that hit us in a short period of time the water table level is getting higher. Even if it only gets temporary higher that is still bad news for homeowners. In these cases, regular basement waterproofing performed from the outside may not help to remedy the situation.

A high water table is something you should take seriously. It can impact your foundation's stability and overall home comfort.

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No matter how far we’ve come with our design and overall construction capabilities, some things are still problematic even for the best of engineers. Namely, high water tables cause nightmares all over the country. In most homes, it lies just above the crawl space or the basement floor level and that’s okay. The problem comes if the surrounding soil on your lot is dense and absorbent.

As such, the issue with a high water table will take time to affect your home negatively. However, when it does, it will allow groundwater to pass through your foundation, eventually inducing water-related damage and serious structural problems. Unfortunately, there’s little you can do to prevent these issues from happening once the water table rises to a certain point. Even some solutions like regrading your yard may not work if things have gotten out of hand.

Here, we will further explain how high water tables function and how you can prevent damage from happening. We’ll discuss what it is, different types, as well as how to measure the one on your property.

What Is a High Water Table?

The first thing we need to discuss here is what a high water table is. Only then can we go into detail about how it can affect you and your home. That said, a high water table refers to a state when the rock and surrounding ground materials join the upper soil layer due to an excessive amount of water beneath it. This phenomenon can occur when there’s heavy rain in the area or when the water from higher elevations spreads into the soil surrounding your home.

High water tables are pretty common in low-lying areas that have soil with poor drainage. However, this can happen elsewhere too. During seasonal changes when there’s more rain, the excessive water can push the rocks and soil upwards too. High water tables are typical when there’s severe flooding in your region.

Different Types of Water Tables

Depending on the geological formations in your area and the season, you can come across different types of water tables. So, to be able to deal with them in one way or another, you’ll need to differentiate them. Here’s what you need to know.

Perched water tables: This type of water table will form when the groundwater gets inside the pockets of the earth’s crust and is unable to leave. In other words, perched water tables restrict water from going further into the ground to reach the normal subsurface groundwater level. This type of water table consists of bedrock material (hard rocks) or heavy-compact clay. Your home won’t be safe even if it’s on higher ground.
Seasonal high water tables: The second type of high water table can occur due to seasonal changes. Namely, during late winter and early spring, groundwater levels will rise because of melting snow and high rainfall. Once this happens, the water from the surface will penetrate the ground and push the water table up. In case you notice that the water isn’t draining away in your yard, you should consider that you have a problem with seasonally high water tables.

How Can a High Water Table Affect My Home?

There’s no point in describing what high water tables are and how you can differentiate them if we don’t mention how they affect you; or to be more precise, we should go into how they endanger the safety of your home and its foundation. Hence, we’ll now talk about the two major issues they cause.

Foundation shift: In areas where the water tables are sitting close to the surface of the ground, it’s not unusual for the groundwater to apply pressure on the lower side of the buildings’ foundation. Experts call this phenomenon hydrostatic pressure. This type of water/soil pressure will cause the bottom of your foundation to crack and allow water through to the inside of your basement or crawl space. In extreme cases, hydrostatic pressure will shift your foundation, causing serious damage to its walls and decks.
Humidity issues: As we’ve said, a foundation can shift in more extreme cases, but that doesn’t mean that you’re safe if it doesn’t. You could still have problems with humidity. These high levels of moisture will foster wood rot, rust, and even mold growth. Hence, the more wood you have down there, the more of a chance you’ll experience costly damage to it.

How Do You Measure the Water Table on Your Property?

You have two main options for measuring the water table around your home. The first one consists of using tape and measuring the level of water in a shallow well. But if you don’t have a well, you can use acoustic or electric probes. Still, we’d suggest that you call a professional to assess the situation in your yard because it might get too confusing.

What Can You Do About a High Water Table?

The best thing you can do to deal with a high water table on your property is to contact a professional and let them handle it. To better understand what they will do around your home, we’ll list a couple of solutions they might opt for.

Yard drainage: The first and most obvious choice would be to install a surface and subsurface drainage system. The drainage will be able to channel the water away from your foundation. This way, stormwater won’t infiltrate the lower levels of your building and weaken the overall structural integrity.
Underground pipes: If surface drainage isn’t enough, professionals might opt for underground pipes or weeping tiles. The builders will lay them onto a gravel bed or a trench that’s below the soil grade. Pitching slightly towards the discharge point, this system will capture any water that tries to infiltrate the soil.

Swales: With the use of swales, you’ll be able to get rid of excess water as it will go directly into the municipal drain. Depending on the grading of your yard, the builders will place them facing the front or the rear end of your lot.
Waterproofing: Lastly, you can opt to waterproof your basement and foundation. In our eyes, this might be the best choice when it comes to high water tables since the combination of sump pumps and interior drains work perfectly together in mitigating water-related damage which is more than common in both Alabama and Tennessee.

In case you’re having trouble with high water tables, you should contact professional help at AFS. Our team is more than capable of providing you with a free inspection and estimate, as well as waterproofing your basement. With their help, you’ll be able to enjoy your home safely once again.

Publish Date: August 7, 2021

Last Modified Date: August 7, 2021

How do I reduce the water table in my house?

How to Lower a Water Table.

Install a groundwater well or use an existing well on your property for the project. ... .

Place a submersible pump in the groundwater well. ... .

Measure the depth to groundwater in the well before you turn on the pump. ... .

Turn the pump on and estimate a stable pumping rate that the aquifer can sustain..

How long does it take for a water table to go down?

It lasts for ten days to two weeks, and it is weather-driven. When you get heavy rain, the area outside your foundation walls (backfill area) fills up with water. Why does it fill with water?

How can a water table become raised or lowered?

Fluctuations in the water table level are caused by changes in precipitation between seasons and years. During late winter and spring, when snow melts and precipitation is high, the water table rises. There is a lag, however, between when precipitation infiltrates the saturated zone and when the water table rises.