What It Costs to Replace Cast Iron Pipes Under a DFW House
Bradley Earp, Responsible Master Plumber, TSBPE M-43562
Replacing cast iron drains under a house in Dallas-Fort Worth is priced the same way every time at MasterTex Plumbing & Drain: the 5-foot tunnel minimum, additional tunnel feet under the slab, the access holes we dig beside the foundation to start the tunnel, plus any yard section that is trenched to the city connection. You can estimate your own job from those published numbers, and the written quote shows the same breakdown.
Every job starts with a $97 diagnostic and a written quote before any work begins, with a camera inspection when the line needs one. We're open Monday through Saturday, 7 AM–7 PM, and closed Sunday.
If you want to know why cast iron fails in North Texas or which Plano and Richardson neighborhoods have it, read our guide to cast iron pipes in pre-1980 Plano and Richardson homes. This page is about the cost.
Our prices for under-slab cast iron
- Tunneling under the slab: $3,375 covers the first 5 feet (a 5-foot minimum), then $425 per additional foot. Dug by hand under the foundation from outside, so floors, tile and cabinets stay in place.
- Access hole: $1,150 each. Each pit beside the foundation where a tunnel starts or a connection is made.
- Open trenching in the yard: $180 per foot. Only for the run from the house toward the city connection.
- 15% off when you approve the written quote the same day.
- Financing is available, subject to credit approval.
- Certified Price Review: we'll match or beat apples-to-apples plumbing scopes. It applies to a written, itemized estimate from another licensed plumber, and it doesn't obligate us to match. How Price Review works.
Soil conditions can change the work. Much of DFW sits on high shrink-swell clay — about 74.5% of Collin County's rated soil, per USDA survey data summarized by HGS Engineering.
Spot repair vs. full replacement
Spot repair makes sense when the camera shows one localized break, belly or cracked joint in pipe that is otherwise sound. That is one access hole ($1,150) plus the tunnel needed to reach the break: $3,375 covers the first 5 feet, then $425 per additional foot.
Full replacement makes sense when scale, channeling or cracking run the length of the line. At that point, repeat spot repairs usually cost more over time than replacing the line once. Old cast iron is replaced with PVC drain pipe. (PEX is for water supply lines, not drains.) A sewer or water repipe typically takes about 3–5 days, and the written quote includes the schedule for your house. Sheetrock we open is reinstalled.
The camera video decides which one you need. We show you the footage and mark the problem spots before we price anything.
Worked illustrations from our published rates
These are illustrations built from our published rates, including the 5-foot tunnel minimum, not actual jobs. Footage is for illustration only. The live sewer calculator and the older sewer-cost guide may still show a straight $425-per-foot line without the minimum; the written quote uses the minimum below.
Illustration 1 — under-slab drains only, 1960s ranch. The cast iron under the house is scaled and channeled, but the yard line was already replaced.
- 40 ft of tunnel: $3,375 for the first 5 ft + 35 ft × $425 = $18,250
- 2 access holes × $1,150 = $2,300
- Total: $20,550. With same-day approval: $17,467.50.
Illustration 2 — whole system, two-bath 1970s ranch. Tunnel to reach both bathroom groups and the kitchen, plus the yard line.
- 55 ft of tunnel: $3,375 for the first 5 ft + 50 ft × $425 = $24,625
- 2 access holes × $1,150 = $2,300
- 20 ft of yard trench × $180 = $3,600
- Total: $30,525. With same-day approval: $25,946.25.
Illustration 3 — 1960s Richardson Heights home.
- 45 ft of tunnel: $3,375 for the first 5 ft + 40 ft × $425 = $20,375
- 2 access holes × $1,150 = $2,300
- 15 ft of yard trench × $180 = $2,700
- Total: $25,375. With same-day approval: $21,568.75.
For yard-only and main-line examples, see our DFW sewer line replacement cost guide. For a number based on a floor plan close to yours, use the sewer line cost calculator. The written quote, not the calculator, is the price.
How many feet a typical house needs
Square footage alone doesn't set the price. Tunnel feet do, and tunnel feet follow the drains.
- Bathroom groups. Each bathroom group and the kitchen tie into the main under the slab. Every branch being replaced adds tunnel footage.
- Layout. When bathrooms and the kitchen share a central wet wall, the tunnel is usually shorter. A split-bedroom plan with baths at opposite ends of the house usually needs more.
- Where the main exits. The farther the main has to travel under the house before it leaves the foundation, the more tunnel it takes.
- Access holes. A typical ranch home usually needs one or two.
A partial under-slab run is often 20 to 30 feet. A whole two-bath house is often 50 feet or more. Your camera inspection measures your actual line, and the quote is built from that measurement.
Tunneling vs. opening the floors
There are two ways to reach pipe under a slab: go under it from outside, or break through it from inside.
We tunnel from outside. Your floors, tile, hardwood and cabinets stay where they are, and there is no jackhammering inside the living space. You'll have limited drain use on the day the new line is tied in.
Breaking through the slab from inside moves part of the cost into flooring removal, dust control, concrete patching and replacing finished floors, and it usually means more time with the house torn up. When you compare quotes, ask whether the floors are being opened and who pays to put them back.
In the yard, open trenching is $180 per foot. Where an existing yard section is still round and the route is open, trenchless pipe bursting can replace that section without a full-length trench. That applies to the yard run, not to drains under the house.
Why we replace instead of lining
MasterTex Plumbing & Drain does not line cast iron pipes. Under the slab we tunnel and replace the old cast iron with new PVC. For suitable yard sections, we may use pipe bursting, which pulls new pipe through the path of the old one. Those are the methods our published prices cover, and they are what your written quote will include.
Comparing quotes
To compare two quotes apples to apples, line up:
- Feet of tunnel under the slab, including the 5-foot minimum
- Number of access holes
- Feet of yard trench (or bursting) to the city connection
- Whether the floors are opened inside the house
- Replacement material (PVC for drains)
- Permit and inspection
Whose line it is matters too. In Plano, Richardson and Garland, the homeowner owns the sewer line from the house to the city connection, and everything under the slab is the homeowner's. Our pre-1980 cast iron guide has the city-by-city details.
If another licensed plumber gives you a written, itemized estimate for the same scope, send it through Price Review. Approve our written quote the same day and it's 15% off. Financing is available, subject to credit approval.
You can check any Texas plumbing license, including ours (M-43562), with the Texas State Board of Plumbing Examiners.
Frequently asked questions
How much does it cost to replace cast iron pipes under a house in DFW?
Tunneling starts at $3,375 for the first 5 feet, then $425 per additional foot, plus $1,150 per access hole and $180 per foot for any yard trench. As an illustration from those rates, 40 feet of tunnel and 2 access holes is $20,550, or $17,467.50 with same-day approval. A sewer or water repipe typically takes about 3–5 days.
How much does it cost to replace cast iron pipes with PVC?
The PVC replacement is included in our published prices: $3,375 for the first 5 feet of tunnel, then $425 per additional foot, $1,150 per access hole, and $180 per foot in the yard. Your written quote lists the feet and holes for your line.
Is it cheaper to spot-repair cast iron or replace the line?
If the camera shows one localized break in otherwise sound pipe, a spot repair through one access hole is usually cheaper. If scale and channeling run the length of the line, full replacement is usually cheaper than repeat repairs.
Do you have to tear up my floors to replace pipes under the slab?
No. We tunnel under the foundation from outside, so floors, tile and cabinets stay in place. You'll have limited drain use on the day the new line is tied in.
Do you line cast iron pipes?
No. We don't line pipes. We replace under-slab cast iron with PVC by tunneling, and we may use pipe bursting for suitable yard sections.
How does the $97 diagnostic work?
Every job starts with a $97 diagnostic and a written quote. We find the problem, show you what we found, and give you the price in writing before any work begins.
Is financing available?
Yes. Financing is available, subject to credit approval.