Reliable access to clean water is one of the most fundamental aspects of rat care, and the delivery method you choose affects hygiene, convenience, and your rats' comfort. Ball-bearing water bottles mounted to the cage exterior are the most common choice. They keep water clean and free from bedding contamination, and they allow you to monitor water consumption by checking the level throughout the day.
When selecting a water bottle, look for a stainless steel drinking tube with a smooth ball bearing that dispenses water without excessive dripping. Glass bottles are preferable to plastic because rats will chew through plastic given time and opportunity. If glass bottles are not available in the right size, choose heavy-duty plastic and inspect it regularly for gnaw marks or cracks that could cause leaks or spills.
Open water bowls are an alternative that some owners prefer, arguing that the drinking posture is more natural and comfortable for rats. Heavy ceramic bowls or bowls that clip to the cage wall are the most practical options, as freestanding lightweight bowls will be tipped, moved, and filled with bedding within hours. The trade-off is that bowls require more frequent cleaning and refilling than bottles.
Many experienced keepers offer both a bottle and a bowl, giving their rats a choice. This also provides a backup water source — if one bottle malfunctions or becomes blocked, the rats are not left without water. Whatever system you use, clean it thoroughly every two to three days. Biofilm builds up inside water bottles and tubes, and a bottle brush small enough to reach the interior is an essential cleaning tool.