How To Look At A House

McGarry and Madsen's home inspection blog for buyers of  

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Does a home inspector check the plumbing under the floor slab?

Thursday, October 25, 2018

There are two types of plumbing pipes under the floor slab in a modern “concrete slab on grade” home: pressurized water supply pipe and unpressurized drain pipe. Any leakage of the water supply piping, even a small fracture, causes visible problems pretty quickly--whether the leak is in a wall or under the floor slab--because the water pressure accelerates the damage, and we can locate the leak with an infrared camera. See our blog post How do you accurately find a broken water pipe leak under the floor slab? for more info on under-slab water pipe leaks. 

   But a defect in the drain piping, such as tree roots getting into the pipe or cracking from age or impact damage, can be harder to diagnose. We test the drain plumbing primarily by doing stress tests, such as turning on the bathtub and sink faucets and flushing the toilet, all at the same time. Or filling up a sink and checking for leakage around the collar, then opening the drain to look for leaks at the slip joints.

    While our infrared camera will pick up drain pipe leaks located at, or just below, the floor slab but, for all practical purposes, once a pipe heads further down any leakage becomes less detectible with infrared. 

   But there is an alternative. If you have concerns about the underground drain piping, particularly the main drain pipe running from the house across the front yard to the sewer connection at the street, a good person to call is James Freeman, of J. W. Freeman Plumbing. His company, along with many other plumbers in the area, uses a plumbing snake with a video head to evaluate the drain piping in older houses. Starting at a vent pipe on the roof, James fishes the snake down through the house drain system and then out to the sewer connection at the street, checking everything from the inside.

   That’s him in the picture above, doing a followup to a recent home inspection of ours, with homebuyer standing by and watching the video tour of his plumbing system. It can be entertaining to watch as he traverses the pipe bends, occasionally coming upon roaches scurrying away or looming tree roots. And you finish the video inspection with the peace of mind that your drain system is sound--or an additional line or two on the home’s repair list. You can contact James Freeman at james@jwfreemanplumbing.com or (352) 316-3229.  

    Click on any of the links below to read other articles about what is required to be included, or not, in a home inspection:

AFCI •• Air conditioner •• Ants •• Appliance recalls •• Appliance testing •• Attic •• Awnings •• Barns and ag blgs. •• Bathroom exhaust fan •• Bonding •• Carpet •• Ceiling fans •• Central vacuum •• Chimneys •• Chinese drywall •• Clothes dryer •• Dryer exhaust •• CO alarms •• Code violations •• Condemn a house •• Crawl space •• Detached carport •• Detached garage •• Dishwasher •• Docks •• Doors •• Electrical •• Electrical panel •• Electromagnetic radiation •• Fences •• Fireplaces  Furnace •• Garbage disposal •• Generator •• GFCIs •• Gutters •• Ice maker •• Inspect in the rain •• Insulation •• Insurance •• Interior Finishes •• Grading & drainage •• Lead paint •• Level of thoroughness •• Lift carpet •• Low voltage wiring •• Microwave •• Mold •• Move things •• Help negotiate •• Not allowed •• Outbuildings •• Paint •• Permits •• Pilot lights •• Plumbing •• Plumbing under slab •• Pools •• Questions won't answer •• Radon •• Range/cooktop •• Receptacle outlet •• Refrigerator •• Reinspection •• Remove panel cover •• Repairs •• Repair estimates •• Retaining walls •• Roaches •• Rodents •• Roof •• Screens •• Seawalls •• Septic loading dye test •• Septic tank •• Sewer lines •• Shower pan leak test •• Shutters •• Sinkholes •• Smoke alarms •• Solar panels •• Specify repairs •• Sprinklers •• Termites •• Toilets •• Trees •• Troubleshooting •• Wall air conditioners •• Walk roof •• Washing machine •• Water heater •• Water pressure •• Water shut-offs •• Main water shut-off •• Water softener •• Water treatment systems •• Well •• Windows •• Window/wall air conditioners •• Window blinds •• Wiring 

• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •

Here’s links to a collection of our other blog posts about PLUMBING PIPES:

How can I protect my pipes to keep them from bursting during a hard winter freeze in North Florida?

Can galvanized steel pipe still be used for new water lines in a house? 

How can I tell if I have cast iron pipes in my house? 

Why can't a sanitary tee be used for a horizontal-to-horizontal drain pipe connection? 

What is the difference between green and white sewer drain pipes?

Is a washing machine drain hose required to be secured at the standpipe?

What are the abandoned pipes sticking out of the wall in my house?  

What are the code requirements for plumbing vent terminations?

What are the code requirements for layout of drain piping under sinks?

What causes a gurgling sound when a bathtub or sink drains? 

What is a "combination waste and vent" in a plumbing system? 

What is a building trap?  

What is a galvanized nipple?

What are the pipes sticking out near my water valves?

How do you accurately find a broken water pipe leak under the floor slab?

What is the difference between water pipe and sewage (waste) pipe? 

Are plastic pipes (PVC, CPVC, and PEX) safe for drinking water? 

Is a hot water faucet handle required to be on the left? 

What is a dielectric union? 

What's that powdery crust on the pipe connections at the water heater? 

If all the plumbing drains have water in them and you can still smell sewer gas, what's causing the problem?  

How can I tell what type of plumbing pipe I have?

Why is there a flexible accordion pipe under the sink? 

What is the difference between PVC and ABS plumbing pipe?

What is the difference between water service pipe and water supply pipe? 

What are the pipes on my roof? 

• How can I find out what type of water pipe runs underground from the water meter to the house (service pipe)?

What is a P-trap?

Why is old galvanized steel water pipe a problem for homebuyers?

What does polybutylene pipe look like? Why is it a problem? 

• Which water pipes are an insurance problem and possibly uninsurable?

• Can you connect CPVC pipe directly to a gas water heater?  

     Visit our PLUMBING page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.

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