DLP v Coram: IPEC dismisses infringement claim and invalidity counterclaim over shower pump patent

The Intellectual Property Enterprise Court has dismissed both a patent infringement claim concerning electric shower-waste pumps and a counterclaim for invalidity. The court held that the defendant's products fell outside the claims but that the patent was not obvious over three prior art citations.

In DLP Ltd v Coram UK Holding Ltd [2026] EWHC 2448 (IPEC), David Stone, sitting as a Deputy High Court Judge, gave judgement following a two-day liability trial concerning UK Patent No GB 2,446,666, titled "an electric shower-waste pump and control unit", with a priority date of 17 February 2007.

The patent

The patent addressed a known safety problem. Earlier "pump in a box" products sealed the pump and electronics together, but if the pump leaked, the sealed box could fill with water and reach the live circuitry. The claimed solution was a unit with a housing containing a first chamber for the pump, a separate water-tightly sealable second chamber for the control circuitry, and a removable, non-watertight housing cover allowing drainage through the first chamber.

Construction and infringement

The court accepted DLP's submission that "unit" meant a single, complete, self-contained product, rather than merely a collection of the claimed components. It also held that a "removable non-watertight housing cover for closing the housing" required the cover and housing to connect directly. A latch or seal was not required, but the two must touch.

DLP's infringement case treated the wall-mounted flat backplate of Coram's Premium Pump as the removable housing cover, and the optional rigid plastic cover as the housing. The judge rejected this as an unnatural reading. The backplate was fixed to the wall and did not provide access to the internal components, which the parties agreed was the purpose of the housing cover. In the Premium Pump, the backplate and cover did not touch at all, so part of the closing was done by the wall, which formed no part of the unit.

The Bluetooth Pump, whose cover slotted onto the backplate, also fell outside the claims because its backplate was not a housing cover either. A late suggestion that the roles could be reversed would have failed too, since a flat backplate with no chambers could not be a "housing".

Obviousness

Coram abandoned its novelty attack during closing submissions but maintained that the patent was obvious over three citations.

A 1986 German application, Grumbach, disclosed a pump unit suspended beneath a bathtub. Neither expert regarded it as a realistic starting point, and one version depended on a house wall to form the first chamber. Reaching the claimed invention from the other would have required impermissible hindsight.

For Gontar, a 1997 UK application, the court found that all relevant features already formed part of the common general knowledge. Applying Vernacare v Environmental Pulp Products, the skilled addressee would have read it "with interest" but would not have been moved to act.

On Quantum, an agreed common general knowledge product, the court held that adding a second watertight enclosure within an already watertight housing, and then making the outer housing non-watertight, involved illogical steps. The judge found that Coram's expert had fallen into hindsight on this point. Although the question of why the invention had not been devised earlier was relevant, the court declined to draw any inference either way, given the small market was not driven by technical innovation.

Proposed amendments to the claims did not need to be decided, though the court indicated it would have allowed them for the reasons given by the Comptroller.

Expert evidence

Both sides mounted substantial attacks on the opposing expert's independence and expertise. The judge rejected all of them, finding that both experts had come to court to assist. He agreed with DLP's characterisation of the attack on its expert, which included approaches to former employers, as an exceptionally aggressive ad hominem attack. He also observed that a case described by both parties as "simple" had been litigated with extreme positions and procedural manoeuvres on both sides.