usctrojanman29_IHB
New member
[quote author="bkshopr" date=1253832308]After WWII slab construction were cheaper to build vs raised foundation by minimizing labor cost of framing the ground floor. Older homes have the advantage of access to the crawl space to check for plumbing leaks or routing a brand new plumbing line.
For post WWII construction Copper plumbing were laid on the dirt and elbow vertically before pouring the concrete slab over pipes. Builders often did not wrap sleeves over the pipes. Without the sleeves the pipes rub against the concrete when the pipes contract and expand in extreme temperature change.
The most obvious is when taking a hot shower in the morning after a very cold night. When hot water passing through a cold pipe the coefficient of linear expansion due to temperature difference for a copper pipe is high resulting in at least 1/2 of expansion displacement. As the pipe expands below the concrete it bows below the slab. However the part where the pipe rises vertically through the slab the restriction produces scraping between the copper surface and concrete. As years passed the copper lining became thinner and thinner from the constant sanding friction. Eventually the endless cycles of scraping tore a hole on pipe.
To fix it one must find the location of the leak and that is usually around the outer radius of the elbow or other mysterious locations below the slab. Sometime it will take several guesses. To repair the leak it will require jack hammering the slab. Post tension slab would be very difficult because of the steel tendons. At 35,000# psi tension a severed tendon shoots out like a spear at 10x the speed of a bullet.
Pipes will not last forever. For all slab foundations the problem is inevitable. The hope is this does not happen in your lifetime.</blockquote>
The biggest red flag about there being a water leak as you describe is if the water pressure is lower than normal.
For post WWII construction Copper plumbing were laid on the dirt and elbow vertically before pouring the concrete slab over pipes. Builders often did not wrap sleeves over the pipes. Without the sleeves the pipes rub against the concrete when the pipes contract and expand in extreme temperature change.
The most obvious is when taking a hot shower in the morning after a very cold night. When hot water passing through a cold pipe the coefficient of linear expansion due to temperature difference for a copper pipe is high resulting in at least 1/2 of expansion displacement. As the pipe expands below the concrete it bows below the slab. However the part where the pipe rises vertically through the slab the restriction produces scraping between the copper surface and concrete. As years passed the copper lining became thinner and thinner from the constant sanding friction. Eventually the endless cycles of scraping tore a hole on pipe.
To fix it one must find the location of the leak and that is usually around the outer radius of the elbow or other mysterious locations below the slab. Sometime it will take several guesses. To repair the leak it will require jack hammering the slab. Post tension slab would be very difficult because of the steel tendons. At 35,000# psi tension a severed tendon shoots out like a spear at 10x the speed of a bullet.
Pipes will not last forever. For all slab foundations the problem is inevitable. The hope is this does not happen in your lifetime.</blockquote>
The biggest red flag about there being a water leak as you describe is if the water pressure is lower than normal.