This is one of the most popular "industrial" options at Screwfix. It is formulated to sink through standing water to target the source of the blockage directly.
Here’s a good review example for an purchased from Screwfix : industrial drain cleaner screwfix
When chemicals alone aren't enough—especially for external drains or severe obstructions—mechanical tools provide the necessary force. Drain Unblockers | Cleaning Fluids - Screwfix This is one of the most popular "industrial"
Would you like a shorter version, or one focused on value for money? Drain Unblockers | Cleaning Fluids - Screwfix Would
Used this on a badly clogged commercial kitchen drain that had been slowing down for weeks. Followed the instructions carefully (gloves & goggles on), poured it in, left for 15 minutes, then flushed with hot water. Worked like a charm – no plunger or rod needed. Strong stuff, so you need decent ventilation, but for the price and speed, it’s unbeatable. Will definitely keep a bottle in the van. 5 stars.