Just because you can buy it doesn't mean it is legal.

Just because a big box store or local hardware store has items on the shelf for you to purchase does not mean that they meet the latest and greatest Building Code.  The codes are updated and change every three years.   Some of the items that are offered in stores that do not meet code are as follows:
1.        Ionization sensing only smoke detectors.
2.       Photo eye sensing only smoke detectors.
3.       Accordian drain pipe
4.       S-traps

Ionization Smoke Detector

Ionization sensing detectors can very quickly respond to the smoke made by rapidly flaming fires.  An example would be Christmas tree on fire in the living room.

Photoelectric Smoke Detector

Photoelectric smoke alarms will respond to smoke made by slow smoldering fires.  An example would be a cigarette in a couch.

The need to have both types of sensing ability in a detector is recommended by US Fire Administration and also required by building codes.  
'Because both ionization and photoelectric smoke alarms are better at detecting distinctly different yet potentially fatal fires, and because no one can predict what type of fire might start in a home, the USFA recommends that every home and place where people sleep be equipped with either (a) both ionization and photoelectric smoke alarms, or (b) dual sensor smoke alarms (which contain both ionization and photoelectric smoke sensors).'  

You will see devices on the shelves of the local home improvement stores that are ONLY one or the other.  The best ones to have are the dual sensor alarms.  Be sure you are buying the correct ones.  Don't forget to replace any device that is older than 10 years old and change the batteries annually in devices that are powered by 120 volts.  Also, ensure that you have a working carbon monoxide detector on each level of the home as a minimum.  

---

Accordian Drain assembly

These types of drains allow a few things to happen for a home owner.  One, it shows that the plumber you hired is NOT licensed or doesn't care about how a drain looks much less works in the future.  Two, it allows a home flipper to get a project done quickly to put the home back on the market without all those pesky inspections.   Three, and most importantly, it allows for gunk (yes, that is a term) to build up on the ribs and clog the drain.  Code clearly states that SMOOTH WALL PIPES shall be used in drain assemblies.

---

S-trap assembly (left)   vs    P-trap assembly (right)

The purpose of a trap is the make a seal to prevent sewer gases from backing up into the home.  There have been several types of traps used over the years.  We will focus on just one of the types today. 

Use of "S" Traps is both illegal and obsolete as plumbing fixture traps where a "P" trap is required. While not every S-trap will cause trouble, enough of them do that they are prohibited in new construction and remodeling.  Careful planning and layout can allow for proper trap and drain installation.
S-traps are often found in older buildings where there is no venting provided for that plumbing fixture.  Keep in mind that bathroom facilities were not always inside the home.  So what's the trouble?  S-traps easily lose the water from the plumbing trap, especially if the S-trapped fixture is near a toilet or other large plumbing fixture like a dishwasher or clothes washer.  When the larger fixture is draining, the sudden, large volume of water going down the drain creates a vacuum in the drain line that can siphon water out of the nearby plumbing traps.  When an S-trap has lost its water seal, sewer gases pass into the building.  Not only does sewer gas have a terrible smell, but did you know that it can also be explosive?  Sewer gas is methane.  Methane is lighter than air.  It will rise into the home.

It is usually very easy to change a S-trap to a P-trap or even add an air-admittance-valve (AAV) when allowed by local code.  

If you have questions don't hesitate to contact me.  I am always here to help with your home inspection needs in Waverly, Waterloo, Cedar Falls and surrounding areas.  Consulting on individual issues like these is available.