Draining down a property’s water supply system before going on a long holiday or leaving a property empty pending sale is a wise precaution in some situations, especially in cold climates. Here are some considerations:

1. Preventing Frozen Pipes: Draining down the water supply can help prevent frozen pipes and the damage they can cause during winter. When water freezes, it can expand and burst pipes, leading to leaks and water damage.
2. Seasonal Considerations: The necessity of draining down the water supply system often depends on the season. If you’re leaving the property during winter or in a location with cold winters, it’s more critical to take this precaution.
3. Heating: If you plan to keep the property heated while you’re away, it may not be necessary to drain the water supply system as maintaining a minimum temperature can prevent freezing. In this case, you may only need to keep the heating on at a low setting to ensure the interior temperature remains above freezing. It may also be advisable to shut off the main water supply.
4. Water Damage: Draining down the system can also help reduce the risk of water leaks and damage in case of unexpected plumbing issues, such as a burst pipe or a leaking valve. This can be important if you won’t be present to notice and address such problems promptly.
5. Property Sale: If you’re leaving a property empty pending sale, you should consider the local climate and the time of year. It may be advisable to take precautions to prevent frozen pipes or water damage, especially if the property will be vacant for an extended period.

To drain down a water supply system, you typically need to:

• Shut off the main water supply.
• Open all faucets and drain the water from the pipes.
• Flush toilets to remove water from the tanks and bowls.
• Consider adding antifreeze to the toilet bowls and traps.
• If you have a heating system, make sure it is properly set to prevent freezing.

It’s important to consult with a professional plumber or follow local guidelines and regulations when taking these measures. In some regions, there may be legal requirements or recommendations for securing a property when it’s vacant. Additionally, your insurance company may have specific requirements or recommendations for properties left vacant for an extended period.