On Your Guard

Your deck is 14” off the ground. You know it does not need a guard (barrier railing in lay terms). A guard is only required when the deck gets to be more than 30 from grade (plus some other rules that we are not going into right now).

The point is that you feel you want one anyway–after all, a fall from 14 inches in the dark with a beer in one hand and a girl in the other could still be at best embarrassing.

So you install a nice guard around the decks as you can see in the following pictures.

The problem is that once a guard is installed, even though it is not required, it must conform to the current requirements of a guard. The guard is not merely a thing installed to keep you from falling 30 inches. If that was the case, the spacing between the balusters or rails would not have to be so close together. The spacing is such that a small child will not either fall through or strangle themselves in the openings.

So even though this guard was not required the spacings between the rails on the one deck and the balusters on the other should be no greater than 4” per current standards.

Charles Buell, Real Estate Transactions in Seattle

Weir-d Science, how a P-trap works

This picture post will attempt to show how a P-trap functions, or more importantly what makes them function.

Notice how the weir can see the vent opening?

P-traps have for the most part replaced most other kinds of traps—notably the S-trap.  The toilet is one notable exception—it is designed to be siphoning—the more siphoning the better.  You want to hear that glug glug glug.


Many inspectors are under the false impression that merely lengthening the trap arm will eliminate the S-trap, but what this actually does is increase the potential for siphoning of the trap as the slug of water attempts to go down the drain.  It is a similar principle to how a toilet siphons.

Still an S-trap

The configuration still makes an “S,” just an odd shaped S is all.

What makes the P-trap function is the vent, and the rules that guide where that vent has to be. 

Essentially the vent has to be at least two pipe diameters away from the Weir.  The Weir is where water either starts to go down the drain after the trap or stops going down the drain.  So in a typical 1-1/2″ kitchen sink drain that would be a minimum of 3″ away.

The P-trap rules

We also have to be careful to not get the vent too far away from the weir as the trap arm could flood and block the vent–essentially returning the assembly to more of an S-trap. 

The rules of how far away it can be has to do with the diameter of the pipe (trap arm).  The bigger the diameter the longer the weir can “see” the vent.

Charles Buell, real estate inspections in Seattle

The Range Hood Exhaust–as Air Intake

Modern tight houses can easily become depressurized when exhaust fans are turned on. What this means is there is no place for the air to come into the home to replace the air that is trying to leave. If there are gaps around door weather-stripping, or gaps around window sashes or similar locations, the air will come into the home at these locations.  Sometimes even chimneys might be the path for this air.

If we operate and exhaust fan in a bathroom the house becomes depressurized, or an area of “lower pressure.” Areas of higher pressure will tend to make balance with areas of lower pressure, so the air outside the building literally “pushes” its way into the area of lower pressure.

Most houses are not tight enough for the air to not find its way in somewhere, and general infiltration was once allowed to be the source of this air replacement.

This small condo unit was too tight for general infiltration to be the source of make-up air, as was evidenced by its finding a path through the range hood exhaust.

Most range hoods have a back-draft damper in them, but there should also be one in the cap at the exterior of the building as well. You can see in this picture there is no damper—but there is a screen.

Exhaust fan vent termination with no back-draft damper

With two bathroom exhaust fans and the laundry exhaust fan running, the purple/violet colors of the thermal image of the chase and microwave/hood shows cold air cooling the chase and the area around the microwave.


The screen at the exterior cap location did hold a tissue paper to show that indeed air was pushing its way through the microwave/hood.

So, let’s say we “fix” the cap at the exterior with a proper back-draft damper. Where will replacement air come from? General infiltration may still be adequate, it is just easier coming from where it is now. If it is not adequate, the functionality of the exhaust fans will be reduced. In other words, they will make noise but not exhaust enough air from the room. It is like turning a 100-cfm fan into a 50-cfm fan.

For exhaust fans to do their job, replacement air is necessary and is required by modern codes when houses get to a certain point of air-tightness. This one may be at that point, even though it is an older home in that respect.

Some “positive” means of allowing exterior air to enter the home may be indicated if exhaust fans do not function properly after the exterior cap is repaired and its back-draft damper installed.

By Charles Buell, Real Estate Inspections in Seattle

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