Extending the upper storey down pipe to the lower level gutter line benefits.

Improved drainage: By extending the upper storey downpipe to the lower level gutter line, you can ensure that rainwater is efficiently directed away from your property. This helps prevent water pooling around the foundation of your home and reduces the risk of water damage.
Enhanced aesthetics: Extending the downpipe creates a more streamlined and cohesive look for your home’s exterior. This can enhance the overall appearance of your property and increase its curb appeal.
Cost savings: By ensuring that water is properly drained away from your home, you can prevent potential water damage that could be costly to repair. By investing in extending the downpipe, you can potentially save money in the long run on repairs and maintenance.
Increased property value: Improving the drainage system of your home can increase its overall value. Potential buyers will appreciate a well-maintained and efficient drainage system, which can make your property more attractive on the market.
Compliance with regulations: In some areas, extending the upper storey downpipe to the lower level gutter line may be required by building codes or regulations. By ensuring that your property is in compliance, you can avoid potential fines or penalties.