Do I have to replace all the cast iron at once?

No. We often replace one failing run at a time — the section under a bathroom, or the main horizontal run in the crawlspace — and leave sound pipe alone until it needs attention.

Will I be without drains during the job?

For the section we're working on, yes. We coordinate the shut so it's the shortest window possible, and we tie the new PVC back in the same day when we can.

Do you cut concrete if the drain is under the slab?

Yes, when needed. Most of the cast iron we replace is in a crawlspace, but under-slab work is quoted separately because it's more involved.

Is PVC really better than cast iron?

For residential drain lines, yes. It won't rust, it's smoother inside so it clogs less, and it's much easier to service.

How long does a cast-iron-to-PVC job take?

A single run under one bathroom is often a same-day job. A whole-house replacement runs 2–4 days depending on layout and access.

Full labor and parts warranty on our work. If we touched it and it leaks or clogs, we come back.

Heavily rusted cast iron drain fitting with corroded joint in a San Antonio crawlspace — before Out This World Services replaced the run with new PVC drain line

Resource Guide

Why Cast Iron Fails and Why PVC Is the Modern Fix

A straight-talking guide from the owner who installs every job. Drain Line Replacement — Cast Iron to PVC in San Antonio.

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Back to Drain Line Replacement — Cast Iron to PVC

Cast iron drain pipe has a typical service life of 50–75 years. Homes in San Antonio built in the 60s and 70s are hitting that number now.

Cast iron fails from the inside out — the pipe scales up, then rusts through. By the time you see rust on the outside, the inside is already compromised.

Modern schedule-40 PVC won't rust, is smoother inside so it clogs less, and is easier to service if you ever need to open the line again.

1. Cost & Pricing Overview

Typical price range

$1,800–$8,500 (single run) — $6,500–$18,000 (whole house)

What affects the cost

Length of drain run being replaced
Crawlspace access and clearance
Number of fixture connections (toilets, tubs, sinks) being re-tied
Whether vents and stacks need to be reworked
Slab-cut work if any drain is under concrete
Debris removal and disposal of old cast iron

When a quote is required

Bid pricing per project — not hourly. Free estimates within 30 miles of San Antonio.

Want a real number for your home? Request a free estimate.

2. How the Service Works

Here's exactly what to expect from start to finish.

1Inspect the drain run and identify failing sections.
2Bid the replacement — partial run or whole-house — in writing.
3Cut out the old cast iron, install new PVC with proper slope, tie into vents and stack, and test.

3. Common Problems, Signs & Symptoms

If you're seeing any of these, it's probably time to call.

Recurring clogs across multiple drains

When more than one fixture backs up, the problem is downstream in the main drain — usually a cast iron run that has scaled shut.

Sewer smell in the house or crawlspace

Cracked or holed cast iron leaks sewer gas. A camera inspection or crawlspace look confirms it — replacement is the fix.

Visible rust flakes or holes on the pipe

Once you can see through-holes or heavy rust flaking, that section is done. Patching is a short-term fix at best.

Gurgling drains or slow flow

Interior scale in cast iron restricts flow. New PVC restores full drain capacity and stops the gurgle.

Home is 50+ years old with original drains

If nobody has touched the drain system since it was built, you're on borrowed time. Better to plan a replacement than deal with an emergency backup.

4. Frequently Asked Questions

Authoritative source

IAPMO Uniform Plumbing Code — drain, waste & vent standards

Source: IAPMO

Bottom line

Our San Antonio crew has been doing drain replacements for years — I've handled a lot of these besides showers. We work clean in tight crawlspaces and re-slope the new run so you're not calling anyone back for clogs. Full labor and parts warranty. Free estimates within 30 miles of San Antonio.

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Questions about drain line replacement — cast iron to pvc?

Call us. We'll give it to you straight.

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