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Choosing a Rat Blocker: Which is best, Nordisk or Ratwall?

Choosing a Rat Blocker: Which is best, Nordisk or Ratwall?

Rats love drains. They are a hidden highway to access properties unseen and cause costly damage. Rat Blockers, or ‘rat flaps’ are simple devices that stop rodents traveling past a certain point within a drainage system.

Choosing a Rat Blocker: Which is best, Nordisk or Ratwall?

Drainage systems flow from A to B – inherent to all drainage networks is a gradient to achieve this. This flow of water, therefore, carries momentum and it’s this momentum that lifts a valve flap – gravity then closes it.

The blockers are designed so the flap will only lift in one direction – in the direction of flow. As rats live in sewers and drains flow to sewers, then rat valves stop rat traffic traveling up from the sewers (i.e. against the direction of flow).

Most dwellings have one main drainage outlet point before connecting to the main sewer, by installing the Rat Blocker here the whole upstream drainage system is protected from Rat intrusion.

A – Terraced Housing

B – Detached House

C – Main Sewer Lines

Choosing a Rat Blocker: Which is best, Nordisk or Ratwall?


If you have a drainage defect under your house that you don’t want rats to emerge from then a correctly positioned rat blocker will stop them from reaching it yet allow waste to flow to the sewers in the normal fashion.

This is a more economical solution compared to digging up your floor and fixing the defect directly (as typically the defect involved doesn’t affect the drainage but just allows rats to infest your building).

Flow and gravity are constants within a drain, so the valve needs no maintenance.

Rat Blockers

There are lots of different rat blockers out there – twin flap designs, single flap designs, serrated flap designs, convex flap designs, stainless steel designs, plastic designs, push-in designs, and gripping designs.

If you fit the wrong rat blocker to the wrong scenario then you risk rats lifting the blocker, the blocker sticking open or the blocker affecting/clogging the drainage system (which will cause you an additional headache to the persisting rat problem).

Bad rat blockers:

  • Are anything plastic – rats can shred these and chew the flaps until it falls off and is lost into the drain.
  • Are anything with a poor hinge mechanism – drains are harsh environments so a lot of thought needs to be given to the hinge mechanism to ensure it can last many years without sticking.
  • Are anything that reduces the internal dimensions of the pipe – sudden restrictions reduce flow and give solids anchor points to snag on.

Good rat blockers fitted to the right scenarios are incredibly long-lasting and reliable – they don’t clog (unless you really start abusing your drainage system).

Good rat blockers:

  • Have all components made from stainless steel – that way nothing rusts and gums up for many, many years.
  • Have a body design that doesn’t reduce the internal dimensions of the pipe nor introduce any snag points.
  • Have a flap design that requires minimal momentum from the water to lift and which glide over the top of any passing solids.



Metex Ratwall is a cost-effective and robust stainless-steel Rat Blocker that is ideal for installation into underground drains.

  • Easy to install from street level into the main drainage outlet between the property and the main sewer.
  • Suitable for use in 4-inch (Ø100mm) & 6-inch (Ø150mm) drainage systems in PVC, clay, and cast-iron materials.
  • Has a unique external hinge allowing maximum waste flow.
  • The external hinge block ensures that the unit cannot become dislodged and lost into the sewer pipe.

Metex Ratwall is the ideal drain protection as it allows the full capacity of the pipe to be employed and ensures that rats cannot infest your home or property through the drainage system.

Choosing a Rat Blocker: Which is best, Nordisk or Ratwall?

Nordisk TX11

Metex Nordisk TX11 rat blockers are the most advanced and reliable unit available, with a world-leading 100,000 installations Globally.

Metex Nordisk are the only rat blocker to achieve Water Research Centre (WRc) Approval in the UK. WRc Approval is the benchmark within the UK Water Industry and entirely sets the Metex Nordisk range apart from all other Rat Blockers. It ensures recognition in the UK as a product that offers exceptional quality and performance. It is:

  • Easy to install into underground drains by hand or from street level using the separately provided installation pole
  • Made from marine grade stainless steel (316) and is suitable for industrial or domestic use with a wide range of sizes from Ø82 mm to Ø350mm
  • Double, serrated flaps to ensure there is no chance of rats getting past them.

Choosing a Rat Blocker: Which is best, Nordisk or Ratwall?

Metex Nordisk TX11 is already the benchmark Rat Blocker, with stringent VA Approval issued by the Danish certification body, ETA-Denmark, and inspected by the Danish Technological Institute.

  • The TX11 passed a two weeklong test with live rats. Food was placed on one side of the Rat Blocker and rats on the other with a fan to push the food smell towards the rats. No rats were able to pass the unit.
  • The TX11 successfully passed a high-pressure water test and remained intact and operational.
  • The TX11 has been proven to be self-cleaning in normal use, with no snagging!

With many thousands of TX11 units installed and working in the field for more than a decade and a legislative requirement in Denmark, this Rat Blocker has been developed and comprehensively tested.

Fitting a Metex Rat Blocker will prevent rats from accessing the building through the protected drains. However, a Rat Blocker alone may not guarantee the removal of rats already in the property. We recommend consulting a professional Pest Controller to ensure the correct measures are taken to ensure all rats are removed and cannot return. For details of suitable professionals, see our list of Approved Installers.