Drainage pipe has to fall at a consistent, correct gradient along its run, and eyeballing it — or using a standard spirit level that only tells you flat vs not flat — isn't good enough to get it right. The Plumtool Adjustable Gradient Level (PLTG145, $163.63) is a 600mm drainers' tool built specifically to set and check a fall, not just level.
Why a standard level isn't enough for drainage
A standard spirit level tells you when something is dead level or dead plumb. Drainage pipe deliberately isn't level — it needs a consistent fall along its length so wastewater and solids actually move rather than sitting in the pipe, which over time leads to blockages and odour even on a pipe with no other fault. Setting that fall by eye, or guessing with a standard level and a tape measure, is where inconsistent grade creeps in, especially over a long run.
What the gradient level does
It's a 600mm tool built for drainers specifically, letting you dial in and check a target fall directly rather than calculating it with a level and a separate measurement at each point along the run. That consistency matters most on longer runs, where a fall that's correct at one end but drifts even slightly over the length can leave a flat or back-falling section partway along — exactly the kind of fault that doesn't show up until the drain is backing up months later.
Where this fits with other drainage tools
Setting the fall correctly during installation is the preventative half of drainage work; clearing a blockage after a fall problem has caused one is the reactive half — see our guide to drain-clearing tools for that side of the job. Getting the fall right at install avoids needing those tools sooner than you should.
Frequently Asked Questions
Can a standard spirit level be used to set drainage fall instead?
Not reliably — a standard level only confirms level or plumb, not a specific graded fall. Setting fall by eye or with a standard level and separate measurements is where inconsistent grade over a run tends to creep in.
What happens if the fall is inconsistent along a drain run?
Even a slight drift from the correct fall can leave a flat or back-falling section partway along, which doesn't show up as a problem immediately but leads to pooling, blockages and odour over time.
How long is the gradient level?
600mm, sized as a drainers' tool for checking fall along a pipe run.
Is this tool only for new installations?
It's most useful during installation when you're setting the fall, but it's also useful for checking an existing run's fall when diagnosing a recurring drainage problem.