Can Kitchen Waste Go To A Soakaway?
Water from the kitchen sink is greywater: it has some pathogens and a fair amount of organic matter that these pathogens can munch on. It requires proper handling or will give rise to bacteria which can make you and your family sick.
As such, kitchen wastewater must never go untreated or unfiltered into a soakaway. To make it suitable to drain into a soakaway, you must first pass your kitchen sink wastewater through a settlement tank or mulch or straw basin.
To understand why kitchen greywater cannot be drained directly into a soakaway, we first need to know what a soakaway is and how it functions.
An explainer on Soakaways
What is a soakaway?
A soakaway is simply a pit in the ground which helps water seep into the soil. The pit holds the water for some time, allowing it to percolate and preventing its runoff.
Surface water, the water from rainfall, is what drains into a soakaway.
Benefits of having a soakaway on your property:
Situated at the lowest point on your property, Soakaways are a natural defense against flooding. They also relieve the load on the public sewer system and make it less likely to flood in case of extreme rain.
Groundwater from underground aquifers is the most important source of fresh water on planet Earth. These underground aquifers have been fed by rainwater seeping down the soil for millions of years.
But now, as we progressively blanket the planet in concrete, this process is getting hampered. Water that would naturally go into the soil is now running off into rivers and going to the oceans. Soakaways may be one of the few ways we can help maintain groundwater levels.
And lastly, having a soakaway can earn you a rebate on your sewage system bill.
How to build a soakaway?
Traditionally soakaways are just “pits” in the ground filled with broken bricks or rubble. This design, however, has a minimal capacity for holding water before overflowing.
Modern soakaways are built using specialized crates called soakaway crates or attenuation crates placed in a pit whose size varies depending on the number of crates used. The crates are arranged together and placed in the pit before being covered with geotextile and lined by shingles.
Can you build a soakaway on your property?
Sadly, not all soils allow enough seepage to make a soakaway feasible. Alluvial and loamy soils are the best, while clay soils are the worst. Having a soakaway that doesn’t drain well essentially means having a pit that floods every time it rains.
To check if you can build a soakaway at a chosen spot, which must be 5 meters away from any buildings in most states, you need to do a percolation test or perc test.
For this, simply dig a small pit 1 foot by 1 foot by 1 foot in the ground and fill it with 10 liters of water. If the water drains away within 2-3 hours, you’re good to go. If not, try going deeper or choosing another spot.
Soakaways are also affected by seasons, and they don’t work so well in the winter. Proximity to a river or an overall higher water table can cause problems too.
These considerations are even more critical when you are draining kitchen wastewater into your soakaway, as draining greywater into a soakaway that doesn’t work correctly can become a breeding ground for diseases.
Since a soakaway holds water for a while before it seeps away, bacteria can decompose any organic matter present in the water. As rainwater runoff does not have much organic matter, this is not usually a problem.
Kitchen greywater, however, is laden with copious amounts of organic matter from food, which has to be removed before it reaches the soakaway.
Check our other article to learn how wastewater treatment works at the industrial level set by step.
How to Treat Kitchen Greywater?
Before treating your kitchen with greywater, you need to ensure source separation. Source separation means that your greywater must not be contaminated by blackwater.
Blackwater refers to the wastewater from toilets and latrines, and it contains feces and is a health hazard. Blackwater must never find its way into your soakaway, and that is why you need to check the plumbing to rule out any cracks or misconnections that may be contaminating your greywater drainage.
Once you are sure of source separation, you can treat your kitchen sink wastewater. Such wastewater usually contains food debris, oils, grease, and human waste such as skin cells and hair, and you can remove them using one or both of the methods given below.
Using a settlement tank:
Settlement tanks are just large tanks that help purify wastewater to some extent. The way they work is this: wastewater flows very slowly through a settlement tank, allowing the suspended particles in the water to settle down, and the relatively clean water on the top is removed. The sludge at the bottom is then removed separately and disposed of.
However, settlement tanks are costly and require a large amount of space to be built. Another option is by using filtration to remove the organic particles from your kitchen wastewater.
You can filter the debris out of your kitchen wastewater to make it suitable for draining into a soakaway. However, considering that kitchen greywater is full of oil and grease, this must be done in two stages:
Stage 1: Mesh filter
A fine mesh filter at the sink drainage will catch the larger chunks and other debris like human hair.
Stage 2: Mulch or Straw filter
Drain your kitchen wastewater into a vertical pipe fixed into the ground and filled with mulch or straw to act as a filter. The straw will absorb most of the grease, and food particles can be easily removed every few weeks with a shovel and disposed of separately.
If available, use barley straw. It releases a small amount of chlorine as it decomposes, providing some antibacterial action. Now the water should be safe enough to drain into your soakaway.
Stage 3: Bushes
Having well-established bushes or reeds close to your soakaway will also help treat any greywater that flows into it. The plants’ roots will absorb the organic matter and use it as nutrients, further filtering the water.
However, this will mean that your soakaway will get invaded and blocked by plant roots and will require cleaning every few years.
Kitchen sink greywater that has been properly treated can go into a soakaway. There are, however, some things you need to consider before doing so:
If you want to send your kitchen wastewater to a soakaway, you have to be careful about what cleaning products you use. Avoid bleaches, chlorine-based cleaners, products containing strong acids or alkalis, or boron products.
These substances can degrade the soil and pollute groundwater, and sodium salts are known to turn the soil alkaline and degrade it.
Go for all-natural cleaning products. At the very least, use non-toxic and low sodium soaps.
Regulations regarding greywater management vary from state to state. Whether or not you are allowed to send your kitchen greywater to the soakaway depends on the laws in your state.
A study in 2013 looked at different states and their greywater legislations:
States treating greywater as septic:
|New York||West Virginia|
States not defining greywater:
States allowing greywater reclamation:
States permitting greywater reuse:
States allowing residential irrigation only
However, this legal landscape is fast changing. Driven by the looming water crisis and increased water conservation advocacy, more states, especially the south, are moving towards more lenient greywater legislation.
Before connecting your kitchen sink to your soakaway or undertaking other wastewater treatment procedures, please check with your local administration. You can learn more about the pros and cons of wastewater treatment in our other article.