Trap help

I have to be honest, I don’t see alot of non p-traps. This is an S-trap of course, but the drainage was fine. Should I ask for replacement anyway and why?

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Because it will let sewer gas escape.

Because it’s an “S” trap.

It’s not about drainage. It’s about health and safety. . .

And health and safety win every time. Thanks.

Sometimes it is a tough call- especially when the waste inlet is in the floor. In this case it looks like they could have used a sanitary 90 and a p trap. I’d write it.

Not a tough call for me I write them all had three in the same house on Monday. S-traps are notorious for siphoning the water dry. Strictly a NO NO

What about adding an AAV like a mobile hole does? Would be OK then, right?

…and then there is always the infamous S - P trap. Thought I would put this up for a chuckle. Of course I wrote it up as WRONG, Wrong, wrong and just plain silly.:mrgreen: 2007_071030emerick0008.JPG

No, that does not make up for an improper trap. . .


I know you are only trying to be helpful but please be careful not to design or prescribe alterations or repairs to any systems as part of your inspection process.

ALWAYS defer these to the specialized qualified professional contractor and allow them to design the correct repair for the situations you encounter.

BTW here are the AAV codes

Are you certain they would be allowed in your area?

How is this trap a health and safety issue?

It may hold water in the trap and it may function properly.

If anything in my opinion it is not a safety issue, and perhaps not even a health concern, without actual testing.


CDC has a different spin then you on this

**Traps **
A plumbing trap is a device used in a waste system to prevent the passage of sewer gas into the structure and yet not hinder the fixture’s discharge to any great extent. All fixtures connected to a household plumbing system should have a trap installed in the line. The effects of sewer gases on the human body are well known; many of the gases are extremely harmful. In addition, certain sewer gases are explosive.

P-trap. The most commonly used trap is the P-trap (Figure 9.6). The depth of the seal in a trap is usually 2 inches. A deep seal trap has a 4-inch seal.

As mentioned earlier, the purpose of a trap is to seal out sewer gases from the structure. Because a plumbing system is subject to wide variations in flow, and this flow originates in many different sections of the system, pressures vary widely in the waste lines. These pressure differences tend to remove the water seal in the trap. The waste system must be properly vented to prevent the traps from siphoning dry, thus losing their water seal and allowing gas from the sewer into the building.

Objectionable Traps. The S-trap and the ¾ S-trap **(Figure 9.7) **should not be used in plumbing installations. They are almost impossible to ventilate properly, and the ¾ S-trap forms a perfect siphon. Mechanical traps were introduced to counteract this problem. It has been found, however, that the corrosive liquids flowing in the system corrode or jam these mechanical traps. For this reason, most plumbing codes prohibit mechanical traps.

The bag trap, an extreme form of S-trap, is seldom found. Figure 9.7 also shows this type of S-trap.

Traps are used only to prevent the escape of sewer gas into the structure. They do not compensate for pressure variations. Only proper venting will eliminate pressure problems.

Bold is mine and I agree with these staments.

Posibility of loss of trap seal and allowing sewer gas into the home.

Minnesota Rules, Table of Chapters
Table of contents for Chapter 4715

** 4715.0960 TRAPS PROHIBITED. **

No form of trap which depends for its seal upon the action 

of movable parts or concealed interior partitions shall be used.

** Full “S” traps, bell traps, and crown vented traps, are
prohibited. **

Traps shall not be made up with fittings, unless authorized 

by the administrative authority.

Water-cooled grease traps are prohibited. 

No fixture shall be double-trapped. 

Drum traps shall be installed only when permitted by the 

administrative authority for special conditions (laboratory
tables, dental chairs, etc.).

STAT AUTH: MS s [326.37]( to [326.45]( 

Current as of 02/05/04

Thats great info, but I fail to see how its a safety issue.

Should it be replaced? I guess that depends on testing and the complete set up of the waste system, venting, et. cetera. Will home purchaser tear it out, or will it nix a deal considerate of the age of the system?

Well the next question is how old is the house? If its existing and predates current code, is it an issue?

how is sewer gas in the home NOT a safety issue?

These are more common in older homes but are not allowed by current codes.
Report fiindings, explain problem and recommend upgrade for added safety.

So without knowing the age of the home, the assumption is it is not permissable. If it predates existing code, it is not a requirement to upgrade.

It may not even be a safety concern if it is vented and functioning.

How do you know there is sewer gas as methane is odourless?

The traps functionality depends on proper venting. If it ain’t broke don’t fix it.

I don’t require anything. That is the buyer’s decision!

How would you know if it’s functioning?

Hardly the only gas present.

Report findings.

Why would I report something that may not be a concern, if at time of inspection its functioning and the trap remains wet.

I don’t have specialized test equipment which is well beyond the SOP to test for gases.

II. The inspector is not required to:

Because during your visual inspection you noted an S-trap. You’re only guessing that it is functional.

Is your nose special equipment? Nose aside, you’re still guessing.

If you know it’s not allowed in current plumbing installations, why would you ignore it?
Do you also ignore missing downspout extensions?
Do you also ignore other code violations that you are aware of?