Role of the Solenoid Valve

In essence, a solenoid valve is a small valve that operates like a floodgate – opening and closing to control the flow of water. They’re found in appliances all around us, like washing machines, dishwashers, ice makers, and more recently, in touchless faucets. They are also used in larger applications, like fluid power pneumatic and hydraulic systems, motors and larger industrial valves, to name a few.

The way they work is simple: The valve opens to feed water into the appliance, then closes again to hold the water back. For example, when you start the washing machine, the appliance calls for water, and the valve opens, allowing water to fill the drum. After the drum is filled, the valve closes and no water enters the appliance until the first stage in the washing cycle is completed. Depending on the washing cycle used, the valve may open and close a few times during the entire process. At the end of the washing cycle, the valve stays in its default closed position until the next wash cycle is started. Like any other product, solenoid valves are not immune to failure. And when they fail, water comes gushing out – quite literally like opening the floodgates.

Origin and Cause is being called more and more by insurers and law firms to undertake investigations on solenoid valve failures, and we have noticed very distinct patterns in the causes of failure that we thought would be beneficial to our readers.

Manufacturing Deficiencies

IMPROPER CHOICE OF MATERIAL

One of the leading causes for the failure of some solenoid valves is associated with an improper choice of material in the design and manufacturing process. One particularly problematic material, used in a critical component of solenoid valves, is a plastic called POM (Polyoxymethylene), also known as acetal.

Interestingly, acetal is a perfectly appropriate material to be used in water related applications. However, it doesn’t perform well when it is exposed to chlorinated water, which of course, we all have running through our homes and businesses. Contact with the chlorinated water, combined with stresses due to water pressure on the material, causes failure due to a mechanism known as environmental stress cracking. The degradation, which eventually leads to a failure, begins with the formation of tiny surface cracks, which over time grow and finally combine into a large final crack. At that point the water will start to discharge through the pathway created by the crack – like a floodgate suddenly breached.

IMPROPER MATERIAL FORMULATION 

Manufacturers of solenoid valves used in water applications have replaced components made from acetal with fibre-reinforced nylon, which is apparently a more resistant material to chlorinated water. However, failure of solenoid valves still occur due to improper material formulation – which simply means that during the manufacturing process, the material is improperly mixed together, making it more susceptible to failure.

Fibre-reinforced nylon exhibits good chemical resistance, and as its name implies, it’s strengthened with (fibreglass) fibres, similar to reinforced concrete – only the matrix is nylon, and the reinforcements are fibres. Similar to reinforced concrete, a good bond between the matrix and reinforcements is necessary for good strength.

If the materials aren’t mixed and/or processed correctly then the final component will be weak and prone to failure, again, similar to reinforced concrete: If there is no bond between the concrete and the steel then the structure made from reinforced concrete will have limited strength and will eventually collapse. An improper manufactured fibre-reinforced nylon component can exhibit lack of bonding between the matrix and the fibres, which will yield a weak final product with reduced strength.

Although solenoid valve manufacturers are now producing solenoid valves made from more chlorinated water resistant materials, there are thousands of old ones still in service. Of course, not all of them will fail but our experience indicates that a large percentage of them may do just that.

Debris

If we can go back to our gate analogy for a minute, imagine that the floodgate is closing, but just before it shuts completely you wedge a rock underneath; water will continue to flow under the partially closed gate, albeit at a slower rate. Sometimes debris in city water, or calcium deposits, can get lodged, or form, inside the valve and prevent it from closing properly. So while it hasn’t actually failed, the obstruction will make the valve unable to operate as intended (close completely) and water will flow freely through it. As the result of this condition, in the case of a washing machine or dishwasher, water will continue to fill the appliance unimpeded, and having nowhere to go, it will eventually overflow. These are tricky cases to investigate because the debris often washes away by the time we get the chance to examine the evidence.

Freezing

Freezing of a solenoid valve in a residence usually takes place when the appliance is near an exterior wall, and the thermostat is set low or turned off during the cold season. The water supply line to a dishwasher, washing machine or ice maker is always filled with pressurized water, which means that one side of what we called the floodgate in a solenoid valve is also always exposed to pressurized water. If the water in the supply line freezes, it will damage the valve either by mechanical expansion, or it will cause the pressure in the line to build up significantly. Downstream from the ice plug location in the supply line, the pressure will theoretically have nowhere to go, and eventually, will let go at the weakest point in the system, which is usually a soldered joint or the solenoid valve.

HOMEOWNER TIP

Before leaving on vacation, or for extended periods of time, we recommend that you turn off the water supply to your home, drain the system and leave the lowest tap, (usually located in the laundry area in the basement) in the open position to drain the water. As your plumbing system is now free of water, chances of water related insurance claims are practically eliminated. We also recommend that you also leave a tap open on the top floor to prevent a damaging water hammer effect from occurring when you turn the water back on upon your return.

Installation Deficiencies

Water damage from solenoid valves on household appliances are often times associated with installation deficiencies: The fitting between the water supply line and the valve can be tightened incorrectly (cross-threaded or over-tightened), or we often find that the tubing is either not cut straight or is not correctly inserted into the fitting. Such situations can arise when the appliance is initially installed, but also can happen later, during a service call. If the evidence is preserved, a Forensic Engineer will be able to provide an opinion on whether the water damage from a solenoid valve is associated with an installation deficiency or not. However, if the water supply line is removed before we get the chance to examine the joint, the chances for a successful subrogation are significantly reduced. So as always, we recommend that you give us a call as soon as you get notice of the claim, so we can attend the site and complete our investigation, and you can secure your subrogation opportunity.

Less common, is a situation where the solenoid valve is installed backwards – believe it or not, this happens; we’ve seen it done by contractors and technicians. The valve is like a one-way street, allowing water to pass through in one direction only. While it can only be installed correctly in one position, there are a few models that can be installed backwards. If it is installed backwards the valve simply won’t hold water, which will continue to flow through and fill the water compartment of the appliance, and eventually discharge onto the floor.

Take Inaction

Unfortunately, water losses originating from solenoid valves can’t be controlled or prevented, as they occur with no warning signs. As Forensic Engineers, we don’t have control over what the homeowner, or the contractor, does with the evidence after the incident. It is common practice that when someone discovers a water loss, they call in the contractor who installed the appliance or did some service work on it.

They might replace the valve and discard the old one, or disconnect the water supply line, without consideration for the claim, thereby, intentionally or in error, eliminating the chances of a successful subrogation action.

We understand that, often times, insurance claims are made after the water leak was fixed. However, if possible, when you receive the first notice of loss, we suggest that you do these two very important things that can potentially help you recover hundreds of thousands of dollars if done in all of your claims:

1. Advise the property owner to wait until an adjuster or engineer can attend before calling a contractor.
2. Attend the site and document the extent of the damage, as well as the source of the damage as soon as possible.

If we can’t be there the day the loss occurred, just give us a call and we can advise you over the phone on how best to preserve the evidence for a successful subrogation claim.

The most important thing to remember is to leave everything as is until it is properly documented and removed by a Forensic Engineer. These investigations are not always straightforward, and by touching or manipulating the evidence, you could be compromising your subrogation potential.

Download

Dinu Matei, M.Sc., P.Eng.

Dinu specializes in metallurgical, materials and mechanical failure analysis. He has extensive experience investigating and solving complex multidisciplinary problems in consumer products, industrial systems, plumbing components, and residential oil spills. During the course of his career, he has been involved in more than 1,000 failure investigations of various metallic and non-metallic components, and in 23 projects leading to the development of new materials and processes.