Replacing plumbing under a post-tension slab is more and more common.

Post-tension slabs are still relatively new in Phoenix residential construction but becoming more popular with builders.  Consequently, there’s a growing interest in the subject on the part of homeowners who wonder what happens when/if it’s necessary to repair or replace plumbing pipes under the post tension slab of their home. 

(602) 273-7473

The first thing we tell customers is, don’t worry!  We have the knowledge and the experience to do any plumbing repair or installation, even under a post-tensioned slab.

replacing plumbing under post-tension slab in Phoenix homeUsually, when we’re replacing plumbing under post tension slab, it’s due to a slab leak* or other plumbing problem under the slab.  At this Phoenix home, however, installation of new pipes under the slab was not because of a plumbing problem, but was part of a kitchen remodeling job.  The kitchen had a peninsula design and all the plumbing was either on the main kitchen wall or contained within the peninsula. When the home was sold recently, the new homeowners decided they would like to re-design the kitchen and add an island with a sink. 

The picture above shows how the tendons have been located and marked out, prior to sawcutting/ jackhammering the slab.

They called us because we’re one of the few plumbing companies in the Phoenix area who specialize in replacing plumbing under post-tension slab.

tendons in post tension slab are marked at this phoenix home to allow for replacing plumbing under post tension slabTo run water and drain lines to their new island sink, it was necessary for us to remove portions of the concrete slab foundation.  The process of installing the new plumbing under their slab was just as it would be for a repair, including electronically locating and marking the cable lines (called tendons) so we could excavate the slab section by section (being careful not to damage the tendons) until we’d exposed enough of the ground beneath the slab to allow us to install the new water and drain pipes.

The slab was carefully sawcut/ jackhammered to allow us to install the new plumbing.

The tendons in the slab were four feet on center.

new plumbing pipes installed in post tension slab concreteFortunately for these homeowners, when the home was built (in 2000, just about the time post-tensioned concrete slabs were becoming popular with builders in the Phoenix area) the norm for the tendon spacing was four foot (4′) on center.  I say fortunately because many newer homes are being built with the tendons three foot (3′) on center (or less!), which obviously makes it that much more difficult to access the pipes under the slab.

The new plumbing was installed under the remainder of the slab.

To get the required permit, we needed an engineer. 

concrete is cut to replace plumbing in post tension slabThe engineer’s report, along with inspections, lets the city know we’re following all applicable codes and safety procedures.  If you’ve read our other blogs or perused our website, you probably know that we feel permitting is important.  Not only is it a requirement in the state of Arizona, it gives the homeowner the peace of mind of knowing that the job has been done right. 


From this …                                                                             … to this.  A clean finish!

plumbing repair in post tension slab has a clean finishExperience counts…
Besides the care required in excavating the concrete to create access to repair/replace the pipes, strict requirements are also imposed on how the pipes are installed, the trenches are refilled, and the
concrete is repaired.  That’s one reason it’s so important to work with a plumbing contractor who has had experience with plumbing under post-tension slabs.

One more thing …
Something we always discuss with our customers is the additional time needed for dealing with this type of plumbing repair or replacement.  A traditional (non-post tensioned) slab leak repair might take just a day, or two, including inspections.  Even repiping an entire house can usually be done in just a day.  But because of the additional steps necessary where post-tensioning is concerned, a job like this does take longer than a normal slab leak.  For most customers, the extra time isn’t an issue.  Their biggest concern is that the job is done right … and that’s why they call us.

Questions about plumbing problems under the post-tension slab of a home?  Give us a call!  An experienced plumber is always available to answer your questions during business hours.  We’re here to help!

Stevens Plumbing Heating & Air Conditioning
(602) 273-7473

*Slab leak is an industry term meaning a leak in the plumbing underneath the concrete slab of a home.