Best Koi Bottom Drain & Koi Toilet Products (Reviews)

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The Best Bottom Drain for Koi Ponds 2022 (Products Compared)

Bottom drains, or “koi toilets,” are one of the easiest ways to remove muck and fish waste from garden ponds – but which bottom drain products are the best? In this article we take a look at some of the most durable, cost effective, and reliable bottom drains models on the market and compare their overall features.

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Should You Have A Koi Pond Bottom Drain or Not? (Benefits Explained)

best bottom drains for koi ponds
Bottom drains are great for koi ponds, as they remove fish waste, bottom muck, debris, and also help aerate pond water. Public domain.

For most smaller garden ponds, especially those with light fish stocks, a bottom drain is mostly a luxury option that reduces maintenance and helps improve water quality. If your pond doesn’t suffer with large spikes of waste, debris, or bottom muck, the fairly complicated (and expensive) installation of a bottom drain system may not be worthwhile.

However, if you have a particularly deep pond or heavy koi stocks, installing a bottom drainage system is one of the most effective ways to reduce waste from the pond floor. Almost everything that is considered harmful to fish will eventually end up on the floor and start to leech substances as sludge as it decomposes. Performing water changes will only reduce free-swimming substances, and you’d have to vacuum almost daily to keep up with the constant influx of new waste fish produce that settles on the pond bottom.

Having a bottom drain means there is a constant process in place to remove this harmful sludge before it can accumulate and decompose further. This allows for less bottom cleaning, maintenance, and an easier time maintaining better water quality standards that can cause issues with pond fish. On top of this, as you can power a bottom drain with a gravity-fed design, you won’t need to install a water pump on the intake end of the system. The water pump will be installed after the settlement environment, which pulls clean water from the tank and into the main filtration system. This means the pump and filter box will not become constantly clogged with debris, which will make water filtration more efficient and extend the lifespan of the water pump.

How Does a Koi Pond Bottom Drain & Koi Toilet Work? (2 Step Process)

1) Removal of Fish Waste & Muck (All Models)

Although nicknamed koi “toilets,” bottom drains aren’t something fish literally use as a bathroom! Bottom drains work by attracting bottom muck, sludge, and fish waste that settles on the pond floor, usually through a gravity fed design. The bottom drain will be dug-in towards the center of the pond floor, and the drain will be connected via piping to a settlement tank or filtration environment. This set-up is referred to as a ‘gravity fed’ as it’s the force of gravity that causes the water to be transferred from the bottom drain and into the settlement tank. As clean water is pumped out from the top of settlement tank, the missing water is equalized by gravity as it drives water through the bottom drain at the floor of the pond – bringing with it all the waste that accumulates on the floor itself. This constant process of equalization within the settlement tank is what powers most bottom drain systems without the need for an electrical water pump on the in-take.

2) Aeration & Oxygenation (Aerated Models)

On top of a bottom drains waste removal potential, certain models also come with built-in air diffuser plates that can be hooked up to an external air compressor to provide large amount of constant aeration to the pond floor. These types of bottom drains are more expensive in comparison with a basic waste removal drain, but are incredibly useful if you’re constructing a pond with large koi stocks. The installation of an aerated drain is similar to a non-aerated model, with the only difference being an extra (smaller) pipe connection running from the air diffuser plate inlet alongside the bottom drains’ main pipe which will be attached to an external air pump compressor above ground.

Things to Consider When Choosing a Pond Bottom Drain Product:-

1) Aerated Bottom Drain Vs Non-Aerated Drain

aerated bottom drain for fish ponds
If you have heavy koi stocks, having an aerated bottom drain will help provide more oxygen for your fish. Public domain.

Bottom drains and koi toilets come in two varieties; one type providing basic drainage and the other drainage as well as aeration. Both will be able to collect bottom muck and waste, so the decision will be based on your working budget and whether you need extra aeration in place. If you don’t intend to run an aerator separately, and want to keep fish in your pond, choosing an aerated bottom drain is a no brainer. Although not as powerful as some dedicated air compressors, an aerated koi toilet will be able to deliver anywhere from 0.5-3.0 CFM of air movement depending on the air pump you purchase alongside. Obviously, the stronger the air pump, the more aeration potential you’ll have to work with, but this will also increase both the running and purchase costs. If money is no object and you just want the best for your new pond fish, installing an aerated bottom drain with a powerful compressor is one of the best ways to keep them happy in their environment!

If you intend to run an air compressor separately, but still want the benefits of bottom muck removal, installing a non-aerated bottom drain may be a cheaper option. Non-aerated models work exactly the same as their aerated counterparts, working with gravity to drive dirty bottom water away from the pond through your plumbing framework. However, they do not include any kind of air diffuser, so will only need a single pipe leading from the bottom drain to the settlement tank. This means they’re easier, and cheaper, to install in comparison to an aerated model but can still provide all the benefits of waste removal. A good option if you already have an aerator in place, or if you have lighter fish stocks or just debris problems.

2) Bottom Drainage & Air Pump Framework

bottom drain pipe size
Bottom drains are commonly installed with a 4″ drainage pipe and a 0.5-1″ air line for the best operation. Public domain.

As they function best in a gravity-fed system, there will be almost zero pressure (0 PSI) inside the drainage pipe from the bottom drain towards the settlement tank or filter box. This means you can make use of much larger diameter pipework without the worry of pressure issues that can occur in water pump powered set-ups. Water will be moving very slowly through the bottom drain to settlement tank, and the only difference between a 3″ ID pipe and a 4″ ID pipe will be the amount (and size) of solids it can transport without becoming clogged. Even for the smallest of koi ponds we always recommend a 4″ pipe on the bottom drain out-take which connects to your settlement environment, as this will allow for much larger debris to move trough the pipe without hindrance. In-fact, most bottom drains come in two standard sizes – those with 4″ in-takes and 3″ in-takes – with the 4″ models being far more popular due larger waste movement capacity. Since you won’t be running a water pump in a gravity-fed system, at least not on the bottom drain side, you can take advantage of the larger pipe diameters with no loss to efficiency.

In regards to aerated bottom drains, you’ll need to also install a separate pipe alongside the main drainage pipe to provide air to the built-in diffuser plate. Unlike the larger drainage pipe, the pipe which you push through compressed air will be much smaller, with common pipe sizes being between 0.5-1″ inner diameter. The ID will depend on the distance you need to push air and the size of your air compressor, with larger distances and stronger compressors requiring higher diameter pipework.

3) Installation – New & Existing Ponds

The advantages of a bottom drainage system are clear, but it is something best installed in new construction projects and not in existing ponds. A bottom drain will need to be installed right in the center of the pond, and you’ll also have to excavate some of the surrounding soil to place the appropriate pipework to your settlement tank or filter system. This isn’t an easy job when constructing a new pond, and it’s almost impossible to install correctly in an existing builds unless you’re able to completely drain the water, re-home fish, remove the liner, and dig the framework – basically working from scratch! If your water quality is good and waste is kept to a minimum via other means (i.e., vacuuming), a bottom drain isn’t really worth the hassle of installation unless you’re planning on expanding your pond in future.

If you’re starting from scratch with a new pond, installing a bottom drain shouldn’t be much of problem as you’ll have full access to all the internals to plan and design the required plumbing framework.  Here is a great video from Youtube showing the basics for installing a bottom drain in a new pond build:-

The Best Koi Pond Bottom Drain Reviews 2022 (Top Models Compared)

Best Non-Aerated Bottom Drain

1) Dreampond Koi Toilet II Bottom Drain Review

Dreampond’s entry-level bottom drain model which helped popularize the term “koi toilet” to refer to bottom drains in general. The Koi Toilet II is a non-aerated bottom drain constructed from extra durable molded ABS with a standard 4″ out-take on the bottom for rip-ID pipework. Unlike the aerated models here, the out-take of the Koi Toilet II is located at the very base of the unit, which means you’ll need a standard 90′ elbow fitting or similar to get the drain plumbed into the main framework.

The Koi Toilet II is fairly small as far as bottom drains go, being only around 12 inches in length and weighting just 3 lbs (1.3KG). It’s much easier to handle compared to larger aerated models, and would be a good choice for smaller ponds or lightly stocked ponds where space is more important than aeration potential.

The bottom drain features a curved dome on top for smooth wave flow over the surface within the pond, and a thick flange and liner ring for a better fit around the pond liner. As stated, this bottom drain comes with a standard 4″ out-take which means you can take advantage of 4″ ID pipework for better solids and waste removal. A decent amount of space will need to be left under the bottom drain due to the in-take location, as you’ll have to fit an elbow fitting directly under the base. Although you can seal this away with sediment, we always recommend concrete with bottom drains to ensure everything is super secure at the base.

There is no diffuser plate included in this model, which makes installation a little easier but also means you have option for aeration in future. If you’re running a separate aerator, have light fish stocks, or only care about cleaning down the bottom muck, this is a very cost-effective bottom drain option!

Affordably Priced
High Quality Materials
Durable & Easy Installation
1 Year Warranty
No Aeration Potential
  • Aeration: No
  • Outlet: 4″ (depending on model)
  • Material: Molded ABS (Acrylonitrile Butadiene Styrene)
  • Weight: 3 lbs (1.3KG)
  • Dimensions: 12 x 4 x 12 inches
  • Warranty: 1 Year

Best Budget Aerated Bottom Drain

2) EasyPro Aerated Koi Bottom Drain Review

One of the our favorite aerated products is the budget friendly EasyPro Aerated Bottom Drain range. Unlike the model above, this is an aerated bottom drain meaning it comes complete with top diffuser plate that needs to be hooked up with an air compressor for operation, and this addition is reflected in the higher purchase cost. With that said, most aerated bottom drains are rather expensive compared to their non-aerated counterparts, but we found EasyPros’ model to be the best “bang for buck” in terms of cost vs quality. If you’re looking for an aerated drainage system on a budget, this is as great choice.

The bottom drain comes with a very standard 4″ out-take connection for 4″ PVC fittings and pipework. As with most bottom drains, 4″ is the most efficient way to move solids and debris smoothly through a gravity fed system, and is our optimal choice for both aerated and non-aerated products. The in-take can also be reduced to fit a 3″ ID pipe if needed using a reducing male adapter, but this is as small as we’d recommend going for a bottom drain design.

The 4″ out-take is attached to the side of the bottom drain, with a smaller 1/2″ in-take connection on the base of the unit designed for the air compressor. As this is an aerated model, you’ll need to install both your pipework from the drainage out-take to the settlement tank as well as the air pipework to the bottom in-take to get the air diffusers working.

When it comes to aeration, the bottom drain comes fitted with a wide top diffuser plate which sits neatly above a curved dome top. The recommended air compressor strength is 0.5-1.5 CFM, which should be plenty aeration for ponds up to 10,000 gallons or more.  The air compressor would need to be purchase separately, and we recommend the Hakko Linear Air Pump as it’s cheap, easy to install, and works well with these bottom drain specs. Our only concern with the design is the small 1/2″ air connection, which may cause some back pressure to the air compressor depending on the pipe distance and compressor strength. A 1″ air connection is optimal for most bottom drains, but a 1/2″ connection is fine if the air pump is in close proximity and specced correctly.

Overall, a very solid bottom drain option with high aeration potential at a very reasonable price point. A great choice if you’re on the look out for an aerated drainage system but don’t want to break the bank!

Cheap For Aerated Model
Durable & High Build Quality
Decent Aeration Potential
1 Year Warranty
Small Air Connection In-take
  • Aeration: Yes (compressor purchased separately – link)
  • Outlet: 3″- 4″ (depending on model)
  • Material: Molded ABS (Acrylonitrile Butadiene Styrene)
  • Weight: 12 lbs (5.5 KG)
  • Dimensions: 17 x 17 x 15 inches
  • Warranty: 1 Year

Best Premium Aerated Bottom Drain

3) Koi Toilet I Aerated Bottom Drain Review

The original aerated Koi Toilet from DreamPond, and the bigger brother to the standard Koi Toilet II model. This bottom drain is considered by many as the premium standard for bottom drain design, with high build quality, large drainage and air connections, as well as high aeration potential.

The bottom drain features a standard 4″ drainage connection which allows for smooth solid and debris removal through your connected drainage pipe. The sweeping and extremely smooth internal bottom of the product provides very efficient debris movement with little chance of clogging. Adaptors can be used to reduce the connection pipe size, but we highly recommend sticking with 4″ connections for the best performance.

In terms of aeration potential, this bottom drain comes with a large 1″ air connection on the bottom which will provide plenty of air movement when combined with a strong air compressor. The larger 1″ connection in comparison with the EasyPro model reduces the back pressure on stronger air compressors and over larger distances, and allows more wiggle room for additional air flow if needed. The air compressor would need to be purchased separately, and we recommend the Alita Industries Air Compressor Range, in particular the 40 LPM (1.5 CFM) model for optimal air flow without too much back pressure.

Build quality is really good here, with the bottom drain being made from ultra durable molded ABS which is highly resistant to wear and tear. A triple internal check valve is included on the inner air pipe, which helps prevent solids entering the air diffuser pipeline and protects the system from damage. Once this is installed securely with some concrete around the pipework, it should be good to go without any worry of future issues!

A downside of this model is the price, which is slightly higher than other aerated bottom drain models on the market. However, you get what you pay for, and the ultra efficient design and large drainage and air connections means you’ll have some of the best drainage possible for your koi pond.

Overall, a very high quality bottom drain model with great waste movement and aeration potential. Highly recommended if money is no concern and you just want the best performance possible from your ponds’ drainage system.

Great Drainage with Sweeping Design
High Aeration Potential (Large In-take)
High Quality & Durable
1 Year Warranty
A Little Pricey
  • Aeration: Yes (compressor purchased separately – link)
  • Outlet: 3″- 4″ (depending on model)
  • Material: Molded ABS (Acrylonitrile Butadiene Styrene)
  • Weight: 10.5 lbs (4.7 KG)
  • Dimensions: 16.5 x 16.3 x 14.4 inches
  • Warranty: 1 Year

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