Possible Clues:

• Amenity for showerheads (2 words)
• Substance aiding the production of suds
• What gardener does in drought likely to cause a lather?
• It increases sudsing power
• With rates revised more frequently, it can facilitate laundering operation
• It reduces mineral content
• Quality's more frequently found in domestic appliance
• It might go in a tank
• Remover of hardness (eg, from mains supply)
• Rain is more frequently than not used for this when it's too hard