According to the laws of science, every occurrence can be explained scientifically. This is also supposed to apply to plumbing experiences. But sometimes the weird things that happen in a plumbing system are hard to explain.

I have accumulated a list of some of my weirder experiences with plumbing systems. Some may be obvious to you, others may not. These weird experiences would make for good questions to put to fourth– or fifth–year apprentices. Sometimes, it takes more thought to figure out what went wrong.

One of the most recent occurrences was a replacement of a water closet. A 3.5 gpf water closet was replaced with a 1.6 gpf pressure-assisted water closet. Immediately after the installation, there was a water hammer problem in the bathroom. The pipes would bang very loudly. Before the water closet was replaced, the home had no history of water hammer. What happened?

Many plumbers would say you need to drain the water distribution system to recharge the air chambers. While this house had air chambers, all of you know that air chambers don’t do a thing. That wouldn’t have solved this problem.

What occurred was a change in the dynamics of the water distribution system. The water hammer was always there. The old 3.5 gpf water closet had a ballcock to refill the tank. Water hammer is nothing more than the instantaneous increase in pressure. Since the ballcock was working on a pressure differential, it was opening under the increase of pressure. Hence, it was serving as a quasi water hammer arrestor.

When the pressure-assisted water closet was installed, the relief from the ballcock disappeared. In pressure-assisted water closets, a pressure relief valve is built in to control the pressure in the pneumatic tank. When a pressure surge (from water hammer occurrence) hits the pressure-assisted water closet, it just sends the pressure surge back in the direction it came from, resulting in loud banging. The solution for the water hammer was the installation of small (mini) water hammer arrestors under the lavatory.

Trap Seal Mystery

Another experience with a 1.6 gpf water closet was in a Park Department’s house that was being renovated into a historical museum. The water closet was a gravity flush tank type, which is considered one of the best flushing water closets. After the installation, the water closet kept losing its trap seal. Nobody ever saw when it took place since the building was unoccupied most of the time.

During the investigation, it was found that the lavatory in the bathroom had lost about 3/4 inch of its trap seal. The other fixtures were not affected. The water closet was located closest to the building sewer connection.

In this particular case, the building sewer connected to a forced main. It was the last connection before the crest of a hill. On the downstream side of the hill was a vent for the forced main. When the forced main activated, the building sewer connections was subjected to tremendous siphonage. While there was a 3–inch vent for the water closet, rising only 15 feet through the roof, it was not adequate to protect the water closet trap seal.

Since there is only 1.6 gallons of water, the closet must begin its flushing action immediately. Any pressure differential starts the flushing action. Well, the pressure differential can also occur on the drainage connection side of the water closet. With an instant siphon action, the water closet began to flush, hence, losing its trap seal. This is why the water closet lost its seal, while the lavatory did not.

The first test for solving the situation was the removal of the cleanout plug on the outside of the house. With the cleanout open, the water closet trap seal was protected. However, when the force main was not operating, the cleanout emitted a wonderful sewer gas odor.

Knowing that the system needed relief from siphonage, a 2–inch air admittance valve was installed in the crawl space just before the water closet connection. That didn’t work either — the 2–inch valve was too small. A 4–inch air admittance valve was installed in its place. The larger valve worked, relieving the siphonic action.

Ghost Flush:

I had a similar experience with a very good flushing 1.6 gpf tank type water closet installed throughout an apartment complex. In the series of buildings, the water closets were supposedly flushing themselves. Upon investigation, there was no pattern to this self-flushing. One day it would be on the third floor in the third building; the following week it would happen on the first floor in the first building.

The owner accused the water closet manufacturer of producing a lousy toilet. He wanted all of the water closets removed.

This was another case of siphon action of the drainage connection that was not protected by the vent. In fact, it was the vent that was causing the problem. The roof vent for many of the stacks terminated in the close proximity of the valley in the sloped roof. Depending on the wind condition, the valley would create a higher wind speed resulting in a strong venturi action of the vent pipe. There was enough change in pressure to start the flushing action.

To solve this problem, the vents could have been raised, but that would have looked ugly. Another method would have been a wind direction device on the vent terminal, or holes drilled in the vent pipe below the terminal. Again, the aesthetics may not be agreeable to the building owner. In this particular complex, these recommendations were rejected. The remaining simple solution was the installation of an air admittance valve in the attic, just below the roof penetration. When a siphon action resulted from the gusting wind, the air admittance valve opened up to allow air in to balance the pressure. Not the real application of an air admittance valve, but it worked.

In a hospital, there was an emergency situation when an operating theater was getting hot water out of the cold water faucet during an operation. Fortunately, this was caught in time to prevent a catastrophe during the operation. This occurrence had never happened before in the hospital.

The problem was the result of the installation of a new detergent dispensing system. The system had a connection that went to the service sink. The manufacturer directed the user to disconnect the system after each use. However, to make it easier, the maintenance department installed a wye fitting on the service sink (one you can buy at any DIY store). The wye fitting had individual shutoffs on each side. They used the wye shut off fittings to control the flow of water, and left the service sink faucet in the on position. The result was a cross flow of water from the hot water to the cold water.

The hospital has since banned the use of wye fittings on service sinks.

In a high-rise building there was a problem of ballcocks blowing apart. The inside guts of the ballcock on a 1.6 gpf water closet were completely destroyed with the water closet leaking continuously.

Although this can occur when there is high pressure in the water distribution system, in this case, the pressure was below the 80 psi maximum permitted by code. The cause of the ballcock failures was air in the water distribution system. The air compressed under pressure. When the water closet is activated, the air expands rapidly as it enters the ballcock. The water in front of the air is blown into the ballcock inner workings with tremendous force. The result is a blown apart ballcock.

The ballcocks had to be replaced and greater care had to be exercised to bleed all of the air from the piping whenever the system is shut down. It is amazing how destructive air can be in a water piping system.

These are just a few of the many wild things you run into in this wonderful world of plumbing. If you dig deep enough, you can figure out the cause of any weird occurrence in a plumbing system. Sometimes what appears to be the obvious tends to obscure the real reason for the occurrence. Other times the obvious is the reason for the weird happening.