Cooking with any amount of grease can be a very messy process. If you leave it unchecked, this waste can build up to form a gross sludge that blocks your pipes and makes it very hard for the water to drain. You may even have to call in a plumber to take your pipes apart and clear out the clog. The grease can also clog the sewer lines within your neighborhood, and this can cause issues at the water treatment facilities. So, you don’t want to pour oils, fats, and grease down your kitchen drain if you can help it.
If you have to pour grease down the drain, you’ll want to have a grease trap, and this article will walk you through what a grease trap is, grease trap installation, maintenance, and benefits below.
More and more homes are adding grease traps to their kitchens to help keep grease, fats, and oils out of the sewage systems. Opening a Grease Trap by Anna Farrell Photography / CC BY-NC-ND 2.0
Defining a Grease Trap
A grease trap is also called a grease recovery device, grease convertor, and a grease interceptor. This is a plumbing fixture that will catch most greases and solids before they get into the sewer waste system. The capacity can range anywhere from 35 liters up to 45,000 liters, and they’re much more popular in commercial operations than in residential ones. Grease traps can be made out of a host of materials, including concrete, cast iron, stainless steel, and plastic. You can put your grease trap outside or inside of the kitchen, and they can be below or above the ground.
How a Grease Trap Works
A grease trap will cool hot or warm greasy water. Animal fats and vegetable oils are usually between 10 and 15% less dense than the water, and they’re also insoluble. By allowing the oils, fats, and grease to all cool, the different layers will separate into layers to make separating them easier. Since the fats, greases, and oils are lighter than the water, they float to the top while the water flows under them and down the drain. The grease trap then catches the oils, greases, and fats. Over time, the solids and grease will build up, but this can block the inlet if you leave it unchecked for too long. So, you’ll want to clean it on a regular basis.
Types of Grease Traps
There are three types of grease traps you can get. The first two, automatic and gravity, are usually found in larger commercial kitchens in hotels or restaurants. The passive hydro mechanical type of grease trap is the one you’ll typically have in your home. Although we’re going to focus on the residential grease trap installation, we’ll touch on the other ones too.
Automatic Grease Trap
Also called automatic grease removal units, these systems use the same system that you’d use in your residential grease trap. However, they re-heat and skim the grease, fats, and oils automatically on a schedule that you set up. The skimmed materials then get transferred to a collection bin to make it easy to remove it and recycle it. The programmed schedule will be based on how much material you produce, and it means that there is no need to check or measure your grease levels routinely.
Additionally, just like the residential system, you can choose from a range of sizes to help accommodate different requirements. They may come with a higher initial investment cost, but they have lower maintenance and running costs while being more efficient.
Gravity Grease Trap
Gravity grease traps are typically bigger in-ground tanks that are made out of fiberglass, concrete, or steel. They also work very similar to a passive setup, but they have a much bigger capacity and work better for high-flow applications. You have to pump your gravity traps out on a frequent basis by bringing in a grease management service company to ensure it runs in top shape.
Passive Hydromechanical Grease Trap (Manual)
The more traditional passive grease trap is the most common one you find in smaller businesses or residential buildings. This is due to the fact that they have a lower investment cost upfront, and the fact that there are several sizes available. So, you can easily install them under most sinks while the bigger units are available to take on bigger wastewater production requirements.
The design of this grease trap dates back to 1885, and this was when the government issued the first U.S. patent on it. Today, these products use the same basic operating design that was on the first 1885 model. They usually feature stainless steel or plastic as the main material, and you have to manually clean them on a regular basis.
Most residential homes have the passive hydrochemical grease trap as it’s much smaller than the other two. This makes it easier to manage. Sam’s Club Recycles Yellow Chicken Grease by Walmart / CC BY 2.0
Grease Trap Installation
Even if you’re not a DIY expert, you may not necessarily have to call in a professional to perform your grease trap installation. A grease trap should be easily accessible so you can clean it out when it starts to fill up, but how often you have to do so is much lower in homes than it is in commercial spaces. The following two steps will outline the whole grease trap installation process:
1. Decide Where You’ll Install the Grease Trap
Generally speaking, the most convenient place for you to install the grease trap is usually right under the kitchen sink. You can also install it outside if you don’t have room inside. Unless you have several sinks in your home that you use to cook with, keeping it under the kitchen sink is usually your best bet.
2. Connect Your Grease Trap
When you bought your grease trap, it came with instructions from the manufacturer. You’ll need to follow the specific instructions for your model as it can vary from grease trap to grease trap. However, each grease trap installation will have three connections to hook up, including:
- First Connection – The first connection will go to the wastewater source or your sink.
- Second Connection – The second connection will connect to the holding tank vent. Most plumbers recommend that you install a cleanout tee before you connect your grease trap to it.
- Third Connection – The final connection is usually located on the lower right corner of the grease trap. You’ll usually secure it to the pipe that leads to your sewage system.
To help you keep your grease trap working after you get it installed and prevent blockages or clogs, you should pour hot water down the drain on any greasy liquid or food particles that go down the drain. This will heat up the grease and help it spread out.
Grease Trap Replacement Costs
Now that you know how grease trap installation works, you should also keep the replacement costs in your mind. After all, there will be ongoing costs associated with keeping it in good working order, but things do wear out. If you notice that your grease trap starts to smell or deteriorate, you may need to replace it and do another new grease trap installation.
If this is the case, you typically want to get in touch with a professional to help with this process. There are a few factors that go into determining how expensive it’ll be to replace your grease trap. The cost of the equipment and tools for this project don’t usually differ much on a national level, but each plumber can charge different rates. The following are the main factors that determine how much this will cost you:
- Average equipment and material costs
- Clean-up prices
- Costs of machinery, components, and surface preparation
- General contractor pricing
- Local inspection and building costs
- Local permit pricing
- Local labor hourly pricing
On average, you can expect to spend between $250 and $1,500 for your grease trap installation and replacement. The costs can seem more expensive at first, but this can be a small amount based on what you’d have to pay to deconstruct it and clean out your pipes if you don’t maintain it.
How To Clean Your Grease Trap
If you have a residential grease trap that you’ve performed the grease trap installation and it’s working well on, this section is for you. You’ll have to clean it routinely to prevent clogs or buildup. To do this, you’ll need the following:
- 2 or 3 garbage bags
- Large trash can
- Oil dry – auto supply stores carry it
- Paper towels
- Rubber gloves
- Scoop and scraper to remove the contents
- Tools to open the trap
- Wooden dowel to help you measure
To start, you’ll need to:
- Make sure you took steps to prepare your work area
- Ensure that you have the garbage bags in the trash can and secured
- Add some oil dry. Oil dry works by soaking up all of the liquid you introduce to it to make getting rid of it easy.
Once you have everything set up, the following steps will help you clean out your grease trap. You can repeat it once or twice a year to keep it in top shape.
1. Use Tools to Detach the Lid from the Grease Trap
If you look under the cover of your grease trap, you’ll notice gaskets. You want to slowly and carefully remove the lid from the grease trap to prevent damaging anything. If you do damage it, you’ll have to replace the gaskets before you can put the grease trap back together.
2. Inspect Your Grease Trap
Throughout the cleaning process, you’ll need to keep an eye on all of the parts you remove and remember how to put them back in the proper place without causing any damage. It’s a good idea to have a drawing of the interior of your grease trap so you have a reference point to make reassembling it easy.
3. Insert Your Measuring Stick
You’ll have to insert a measuring stick in order to tell how full the grease trap is. You should gently insert it and stir it lightly so the grease marks the level on the stick. You want to then remove the measuring stick and record how much grease, oil, and fat is in the system.
4. Remove any Still Water
You want to get a bucket and carefully remove any still water you see. You can pour the water into a larger bucket to reuse and pour back into the drainage after you finish your waste collection process.
5. Remove Solid Waste Using a Scraper and Scoop
Look at the grease interceptor and remove all of the solid waste you see. To make it easier to transport the waste, you can mix it with oil dry. This product works to solidify any liquids, and this includes water. Put this mixture into a heavy-duty plastic trash bag to make it easier to get rid of later.
6. Clean the Sides, Parts, and Lids
Get room temperature water, a pot scrubber, and soap to remove the excess waste from the lids and sides of the grease trap. Once you remove all of the debris, you can use water to flush the screens and parts to get rid of the soap and debris. End by reinstalling the grease trap.
It’s essential that you set up a system to clean your grease trap routinely. How often you do so will depend on how much you use your kitchen. Triangle Grease Trap by Gerry Dincher / CC BY-SA 2.0
Benefits of Regularly Cleaning Your Grease Trap
Regularly cleaning your grease trap is critical to keep it in top shape. When you neglect it, it can cause huge issues. Additionally, your grease trap will intercept the most solids and greases that get dispensed in the kitchen wastewater before it gets to the wastewater disposal system that goes through your plumbing system before reaching your sanitary sewer lines. When you have too much buildup, the lines will get clogged and cause a nasty odor to drift back up.
You can avoid costly, smell, and dangerous situations by routinely cleaning your grease trap after you perform the grease trap installation like we outlined above. The following benefits highlight how important this task is:
Better for the Environment as a Whole
When your grease trap overflows, it loses the ability to catch more grease, and this will allow some of it to get outside into an in-ground drainage field or into major waterways. This can be harmful to the local environment, and it can also be a health hazard. If it gets bad enough, you can get fined.
Costs Less Than Repairing It
Generally speaking, most grease trap systems cost less to maintain than they do to repair. When you neglect your grease trap and it gets clogged, it can easily break down. For example, an emergency repair can put your kitchen out of commission for days, and you’ll pay premium pricing to have a professional come out on an emergency basis to fix it.
Helps the Kitchen Smell Nicer
Imagine all of the debris, gunk, and slime that ends up in your grease trap. If you don’t clean it, it’s going to release a foul smell. This is unpleasant for anyone who uses the kitchen and it can be a health hazard. Regularly cleaning out your grease traps can prevent the odors from building up, and this makes your kitchen smell nicer.
Keeps the Kitchen Functioning
Grease, oils, and fat backups are one of the most common issues you’ll face after the initial grease trap installation. When the interceptor gets too full, the grease, fats, and oils will start to flow back up to the drain. This can cause a mess that is very expensive to clean and eventual expensive repairs.
Cleaning the grease trap can prevent backup and clogs. When you have too much grease, oil, or fat in your grease trap, they can easily clog. Not only does a clogged system reduce how well it works, but it’ll eventually cause the whole system to back up into the drain.
Grease Trap Maintenance
Grease trap installation is only a small part of the process you have to follow to keep your grease trap in top shape. There are several steps you can take to help maintain it so you can go longer between cleaning sessions. They include but are not limited to:
Clean Spills Right Away
It’s easy for spills to happen when you’re making your lunch or dinner in your kitchen, and you should clean them up straight away. Soups, sauces, cooking oils, and other food items that have grease should get cleaned up as soon as you notice them. If you don’t, the grease can get into the drain and create a slip hazard. You should clean up greasy food spills using towels that you toss into the garbage. Don’t mop a greasy spill toward any floor drain you have.
Don’t Use Disposals
Most commercial kitchens and a lot of residential ones don’t have garbage disposals or food grinders anymore because they allow ground up food to slip through the sink and into the pipe system. The food is very likely to cause clogs somewhere, and it can lead to damage or backup. You should keep these things out of your kitchen and follow the maintenance steps we outlined above to keep the food away from your pipes.
Hang “No Grease” Signs
Hanging up small “no grease’ signs above your sink or any appliance you use to prepare food or wash dishes can serve as a reminder to anyone who cooks to not pour oils, fats, and grease down the drain. You should put a sign wherever you need it in your kitchen.
Install Screens Under Your Sinks
Even though scraping your plates will get most of the food particles and debris in the garbage, there could be grease or food residue left, especially after big gatherings. This is why you should have screens installed under your sinks. The screens will help to ensure that any grease or food left over on your dishes will get filtered from the water that goes through the sink. In turn, this protects your pipes. If you routinely cook dishes that contain smaller grains like corn and rice, these screens are very helpful for keeping them contained.
Scrape All Plates
One great way to stop grease, fats, and oils from washing down your drains in the kitchen is to stop them from getting into the sink in the first place. You want to carefully scrape all of the food of your plants and other dishes using a rubber spatula before you put them into the sink.
Scraping the plates really well will reduce the amount of grease and debris that can potentially get into your grease trap and clog it. Dirty Dishes by Sean / CC BY-ND 2.0
Watch the Water Temperature
If you’re pouring boiling water down the drain or using hot water to wash the dishes, the water temperature shouldn’t exceed 144°F. Water above this temperature will melt the grease, oil, and fats. In turn, they’ll drain right through the screen in your grease trap and get into the sewer system. The oils and grease will solidify later and cause huge issues in your plumbing system. In commercial buildings, allowing any substances like this to get into your sewer lines will cause you to get fined if you get caught.
Why Professional Grease Trap Maintenance is Critical
If you follow the best practices and keep the grease from reaching your pipes, the grease traps will function as the last line of defense. Any oils, grease, or fats that make it through the screens in your sink will get filtered out by your grease trap installation before it gets to the sewer line and it’ll get caught in the trap’s receptacle. The grease will rise to the top and allow the water to flow out the bottom.
As the oils and grease build up inside the grease trap receptacles, it can restrict how much water can drain. Eventually, the water will back up enough to clog the lines. This is why it’s so important to limit how much grease enters the traps and check your traps regularly to prevent clogging. If the grease traps are clogged, you can experience the following:
- Backups and flooding
- Expensive cleaning or remediation services
- Foul odors invading the kitchen because the odors don’t have an outlet
- Possible safety, health, and contamination issues
Benefits of Having a Residential Grease Trap
A grease trap can be a very valuable addition to your home. If you’re someone who cooks a lot or you flush grease down your sink regularly, you’re going to want to know the benefits of grease trap installation. There are two main ones, and they include but are not limited to:
Grease traps help reduce pollution, and this keeps the environment clean. When you cook without one of these traps installed, the grease, fats, and oils can flow into local rivers, streams, and ponds. This can get toxic as it builds up. A grease trap will catch these contaminants before they reach the sewage system. Also, you can convert fats, oil, and grease into a very rich mulch that you can use as fertilizer.
Having a grease trap installation will reduce the number of expensive maintenance and repair projects you have to undertake due to blocked pipes. As long as you maintain your grease trap properly, you won’t have to worry about your sewage system getting blocked. Also, maintaining them is hassle-free, and cleaning them is easy.
We’ve outlined the common steps involved in grease trap installation, benefits, how to clean and maintain it, and more. You can now decide if you want to install one of these helpful components in your home.
Jen is a master gardener, interior designer and home improvement expert. She has completed many home improvement, decor and remodeling projects with her family over the past 10 years on their 4,500 sf Victorian house. She is also a passionate farmer who keeps goats, chickens, turkeys cows and pigs on her farm, and an instructor for her community’s Organic and Sustainable Farming project.