How to Repair the Main Stopcock

The house stopcock, or shut off valve, controls the mains flow of cold potable water into the property. It is commonly located under the kitchen sink although it may also be installed near a front door, in a cupboard, or even under a floorboard. It would be uncommon to find more than one stopcock controlling the mains water supply into an individual property.

Most stopcocks have to be manually operated, although there are now some being installed that are electronically operated. Electronically controlled stopcocks require specialist maintenance and should not be serviced by the householder.

It is most important that the householders are able to locate, identify and operate the manual stopcock. This is because it is the most practical way of closing off the pressurised mains water supply into the property. This would need to be carried out quickly in the event of a water leak or burst pipe within the property. It might also need to be operated to facilitate water appliance repairs or installations.

Perhaps the biggest problem that occurs with mains water supply stopcocks is the inability to turn them off. This is due to infrequent use. Without a frequent operation, the internal mechanism becomes affected by mineral particles and substances produced by the effects of metal corrosion. These adhere to the surfaces of the moving parts. Over time, this causes the washer and jumper mechanism to seize up. The crutch head becomes very difficult, if not impossible to turn. In the panic of a plumbing emergency, it is not uncommon for a householder to apply excessive force to the crutch head of a seized stopcock. Unfortunately, this can result in the crutch head shearing off from the spindle, leaving the valve in the open position.

It is also important to ensure that the operative knows which direction of turn opens and closes the stopcock. It is not unusual to find a householder has sheared off the crutch head by applying excessive force in the wrong direction.

Anti-clockwise opens. Clockwise closes.

To prevent problems occurring with a stopcock, it is a good idea to turn it on and off regularly. This will help to prevent a build up of material and ensure that the mechanism operates freely. It is also a good idea to turn a freely operating stopcock fully on, and then give it a half turn clockwise and leave it at that position. This will provide a little extra play on the device should it become stiff to operate in the future.

To free a seized or difficult to operate stopcock, spray a little penetrating and lubricating oil onto the spindle and gland nut, and then leave it to seep into the mechanism. This should solve the problem. If that does not work, slacken the gland nut and apply the spray again. If the stopcock still refuses to operate, a small amount of force can be applied to the crutch head using a wrench.

Occasionally, applying a carefully directed blowtorch flame to the gland nut will provide just enough metal expansion to free the seized mechanism. It is a wise precaution to clean away any surplus penetrating oil before doing so.

If all attempts to free a seized stopcock fail, the water supply can be turned off at the water supplier’s main valve. This will usually be located outside the homeowner’s boundary. It may be on the pavement under a small iron cover marked SVS, or it may have the water suppliers identifying mark. Sometimes this valve is a normal stopcock, but more often than not it is a spindle headed valve that requires a specific tool to operate it. This can be obtained from tool hire firms.

Alternatively, the water supplier will attend to operate the device. This mains stopcock is the property of the water supplier and its maintenance and operation are technically their responsibility.

On some networks, turning off the water supplier’s mains water valve will affect other residents. They should be forewarned about any interruption to their supplies.

Turning off the water supplier’s mains supply valve will facilitate the repair or replacement of the domestic water stopcock. It is quite feasible for a competent DIY enthusiast to strip down and service a mains stopcock or to remove and install a new one. However, the location of the stopcock may make access and work on it difficult due to restricted working space.

When removing and replacing a domestic mains stopcock, there will be a significant amount of water and pressure remaining in the system when the supplier’s valve has been turned off. This pressure can be released by turning on the domestic cold-water tap. Unless a drain valve has been installed close to the stopcock, a suitable receptacle will be required to collect any surplus water draining from the pipe above the stopcock.

On other occasions, a householder may become aware of a slow leak from a stopcock. Left unattended, a small leak can cause substantial damage to the fabric of a property. The most usual causes are leaking compression nuts or deterioration of the gland packing material.

Leaks from the compression nuts can be addressed by gently tightening the nuts. Care should be taken to not over-tighten compression nuts, as this will interfere with the correct operation of the stopcock. The stopcock should be held firmly with a set of grips whilst tightening the compression nuts to prevent fracturing the attached pipe-work.

Leaks from the gland head can be rectified by trying to tighten the gland nut. If that fails to stop the leak, removing the crutch and unscrewing the gland will allow the householder to clean away any detritus and old packing material. It is not necessary to turn off the water supplier’s main valve to accomplish this task. PTFE tape can then be gently wound around the exposed area of the spindle and prodded down into the gland area with a screwdriver. The gland nut and spindle can then be re-attached.

In general, the regular inspection and operation of the domestic mains stopcock will ensure problems do not occur, or only become apparent in an emergency.

Because of the substantial damage that can be caused by unmanageable releases of water under mains pressure and the subsequent insurance implications, if there is any doubt over issues relating to competency, professional assistance should be sought in relation to stopcock operating issues.