How Do I Know If I Should Get a Manual or Automatic Grease Trap?


The FOG problem still looms large. Fats, oils and grease (FOGs) are still making their way down our drains and into our sewers where they clump together and form fatbergs over time.

Water companies are still footing the bill for removing most of those bergs, as they focus on spreading awareness about the FOG problem – giving food businesses the benefit of the doubt while gently encouraging better practice.

But it won’t be long before their focus shifts. We’ve seen food businesses fined thousands of pounds for poor grease management practices, and we could see many more financial penalties handed out to unwary businesses in the coming years.

Ignoring the fatberg problem is bad for business – and getting a good quality grease trap installed is an investment worth making.

Would You Pay £2000 to Save £8k?

But, with so many to choose from, where do you start?

Let’s begin with the basics.

There are two types of GRU to consider.

The Manual Grease Trap


Image 1:Stainless steel manual grease trap exterior. Image 2: Stainless steel manual grease trap interior with solids filter. Image 1:Stainless steel manual grease trap exterior. Image 2: Stainless steel manual grease trap interior with solids filter.


Also known as Passive traps, Manual stainless steel grease traps have no moving parts and don’t need electricity to run.

Tucked into a corner of your kitchen beneath sinks or concealed beneath a drain cover as an underground grease trap, manual traps live in a gap in your drainage pipe, between your sinks and appliances and the sewer outside, intercepting the flow of wastewater out of your kitchen.

They slow the flow, allow the wastewater to cool and separate into three layers: FOG, solids and clear water.

While clear water escapes through the filter into the outlet, the solids sink to the bottom of the trap while the FOG forms a layer up top.

As the FOG and solids collect, you’ll need to clean your manual trap out – ideally before it reaches 25% capacity and certainly before the FOG and solid waste begins to decompose and give off that infamous smell.

Many food businesses opt to employ professionals to pump their traps on a regular basis, though some do the cleaning themselves: scooping out the FOGs and solid sediment before pumping out the water and washing the trap with a healthy dose of disinfectant.

If this DIY cleaning operation seems like a tall order but you don’t want to pay for professionals to do it for you, investing in an automatic grease trap.

The Automatic Grease Trap


Image 1: GreaseMaster GM50 Automatic Grease Recovery Unit exterior. Image 2: How the GM50 works. Image 1: GreaseMaster GM50 Automatic Grease Recovery Unit exterior. Image 2: How the GM50 works.


Automatic grease traps or automatic grease interceptors (AGI's) may be the answer. 

Like manual traps, automatic traps sit in the midst of your drainage pipe, intercepting the flow of wastewater from your appliances and sinks into the sewers outside. Like manual traps, they slow the flow of wastewater and allow it to cool and separate out into layers.

But, automatic traps go one step further to make the clean-up process easier. An external strainer catches most of the solid waste into a collection bin while the automatic system works on a programmed schedule to re-heat the FOG waste in the trap so that it can be skimmed out into another collector bin, for easy removal and recycling.

These benefits do come with some cost, however: not only are automatic traps more expensive, but they also require electricity (which costs a little extra money) and you’ll need to give them at least 10 minutes of TLC every day, emptying and washing out those waste collection bins.

If this doesn’t sound like too much to ask your staff to do, an automatic trap may be for you – but, before you dig deep into those pockets, you’ll need to figure out the following:

What Size Do You Need? Blackboard with geometry

When it comes to grease traps, size matters – particularly for the efficiency of the GRU.

Larger traps are more pricey but go too cheap and small and your trap will fill up too fast – and, once they are over a quarter full they become very inefficient very quickly. A full trap is the same as no trap at all.

To help you choose, figure out your wastewater flow rate in gallons per minute (gpm) – this can be done based on the diameter of your waste pipe - and, if you need to, feel free to ask your supplier for advice. Read more about What Size Grease Trap Do I Need?

Then, think…

How Much Are You Willing To Spend?

Cleaning out a manual trap on your own can be the most cost-effective method of combatting the FOG problem. But, without even mentioning the potential health-risks, the job itself is one which most people dread and put off.

If this is likely to happen, it’s also likely that your trap will spend a lot of its time being full and ineffective, while doing nothing to prevent a fine coming your way.

So, before you go too cheap, think about the alternatives: if you want to make the DIY clean-up operation easier, paying a little more to begin with by investing in an automatic trap may be for you; if, on the other hand, the idea of handling the gunk that comes out of your drains is unappealing, you may want to look into professional pumping.

Then there’s the question of Quality. Always choose a durable stainless steel trap over one with breakable plastic parts, and always check out multiple reliable reviews before you decide which particular trap to trust.

This Christmas, be sure to treat yourself to the GRU which is right for you.