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This page contains a list of Frequently Asked Questions (FAQs) and information about Planter Drainage. The document contains many answers, yet not all the information you may need or require. If you'd like more information regarding Container irrigation, please check the "Container Irrigation & Drainage FAQ." For product information, please go to our website.
Tournesol manufactures planter drainage systems with varying levels of complexity. These products can be used to pump-out planters where no drainage can be tolerated, provide overflow for excess water, and control drainage in many applications. While these are designed to integrate with most Tournesol Siteworks irrigation and containers, they can be used equally well with pots or planters from any manufacturer. First, we want to let you know the varied drainage system options.
Pump-out Systems (DR1 & DR3) –DR1 - Simple pump-out tube and sleeved collection pipe for round and square planters
DR3 - Pump-out tube and sleeved collection pipe for rectangular planters
Pump-out systems are used to manually remove water from planters with no drain hole.
DR1 and DR3 examples:
Tank Adapters (TA & TODA) –
TA - Double gasketed drainage adapter for plumbing drains to liners, boxes, and planters.
TODA - Side discharge overflow adapter.
The Tank Adapter (TA) is the easiest way to connect a drain line to a pot. The TODA adds a manual ball valve to a tank adapter, which allows control of overflow or connecting a garden hose for channeling drainage. These product options are also listed on the Drainage Control Products PDF. The drainage adapter guide lists all options for the adapters.
TODA and TA examples:
Vertical drain example: Horizontal drain example:
Overflow Drainage Adapter (ODA) –
The Overflow Drainage Adapter is a compromise between free draining and not using a drain hole. This option raises the drain hole approximately 3” off the floor of the planter like an internal saucer and is an alternative to both a pump-out system and/or a saucer.
SL = Fiberglass, used with FRP planters
SCL = Concrete, used with GFRC planters
Tournesol Sitework’s FRP and GFRC saucers are sized to closely fit most of our FRP or GFRC containers, whether round, square or rectangle. The attractive return lip of the saucer will extend just beyond the edge of the container. Each saucer has built-in risers to increase the drainage capacity.
Saucer examples - Round, Square and Rectangle:
Yes, we have answers to your questions...
1. Why is drainage important?
Plants require both moisture and oxygen at the root level to survive. Too little moisture, and they die from underwatering. Too much moisture displaces the oxygen and can lead to anaerobic bacteria growth – the “stinky” smell that comes from an undrained pot. An undrained pot left exposed to rain literally drowns the plant.
2. What are my options for drainage?
a. Free draining
3. What is the problem with free draining?
Free drainage will keep the soil from becoming saturated. However, tannin-stained water and minerals may cause some discoloration/staining to occur on the surface below the pot. In public spaces, the drainage water may also pose a slip-and-fall hazard. While free-draining maintenance is easy, regular power washing may be needed to remove staining.
4. How do you keep the weight of the planter from compressing the bottom on the surface below and clogging the drain holes?
Most surfaces are somewhat rough, and don’t seal around the drain hole. However, there are several simple options. Tournesol’s VersiCell Drainage Panels may be used underneath planters to provide full basal support and free drainage. Alternately, a non-degradable and non-compressible material (asphalt or fiberglass shingles, for example) can elevate the planter bottom and create a slight gap between our planter bottom and the surface it rests on. It’s important to support as much of the planter bottom as possible.
5. Are drain holes standard on planters?
It depends on the material the pot is made from. Standard lightweight FRP fiberglass planters do not come predrilled with drain holes. A drain hole is very easy to make with a regular drill in the field and can be made to fit any application. Because they are far more difficult to field install, both lightweight GFRC concrete planters, as well as metal planters come standard with drain holes. The Planter Drain Hole Guide notes our standard drain hole size, location, and quantity of holes depending on the size of the planter.
6. How many drain holes are suggested/required per linear foot of planter?
Tournesol recommends planter drain holes (1 5/8” Dia.) in the quantities shown below, however, the answer also varies depending on the rainfall in your location. Please speak with your sales representative to discuss custom options for other requirements.
Drain hole recommendations - Square, Round and Rectangle:
7. What is the best setup inside the pot to ensure drainage?
For proper drainage, a porous layer at the bottom of the pot is a good addition. Whether a layer of gravel, drainage mat, or our VersiCell drainage panels, the drainage layer will allow better flow out the hole.
8. What are my options if I don’t want the pot to free drain?
There are two options – using a pump-out system or controlled-drainage.
9. What is the pump-out system and what is its purpose?
If water is not allowed to drain out of the pot, then excess buildup must be removed. A pump-out system is what it sounds like. The planter must be ordered without a drain hole, and must be ordered with TourneSeal, a full waterproof coat applied to the inside of the pot. Remember FRP pots are standard without drain holes, GFRC and metal pots are standard with holes. Typically, a pump-out is a large-diameter pipe planted vertically in the soil that allows a siphon or pump to be used to manually evacuate excess water as it builds.
Pump-out systems are common but require regular maintenance during periods of rain. Planters and pots with pump-out systems should be emptied shortly after rainfall; if not emptied, saturated soil will stress the plants. The challenge with pump-out systems is that the maintenance crew needs to be trained to remove excess water to ensure the plants survive and thrive. Removal is most often done with a siphon pump but may also use a shop-vac or other vacuum system.
10. What is TourneSeal, and why is it required with pump-out systems?
As mentioned above, we highly recommend that TourneSeal waterproofing be specified for all pots that do not drain. TourneSeal is a waterproof barrier applied all the way to the rim, which makes the planter 100% watertight. Standard pots include damp-proofing to protect the pot when it is draining, but TourneSeal ensures that a pot that fills up won’t leak.
11. Is there a difference in pump-out systems for different shaped pots?
Our DR pump-out product can be configured in a linear or circular configuration depending on the shape of the planter. Typically, the round version (DR1-X) will be used in both round and square pots, and the linear version (DR3-X) will be used with rectangular pots.
DR1 and DR3 examples:
12. Where is a pump-out system (DR) placed during installation?
The bottom of the DR pump-out system should be placed at the lowest drainage layer of the planter. This will allow the maintenance crew to pump-out excess water after rainfall or excess water from over-watering. The cap of the DR system should be above the top of the soil profile for easy access, usually 2” or more depending on preference. Leave the cap closed to prevent leaves, dirt, and other foreign materials from clogging the pump-out tube.
13. What is controlled drainage?
Controlled drainage allows the excess water out of the planter but prevents free draining. The simplest version of controlled drainage is placing a saucer underneath the pot. There are other alternatives, including plumbed drains and overflow drains.
14. A saucer seems like a good idea – what might be a problem?
Saucers work great, and we sell many. However, some customers object to the look of a tray sitting below their pot. A saucer also has a limited volume of water that it can hold. If it rains too much (or someone overwaters), it can overflow and stain the surface below, just like a free drain. Finally, standing water isn’t something that all owners are comfortable with – check before specifying a saucer.
15. How can we connect a plumbed drainage line directly to a pot?
While many customers can come up with a solution using PVC pipe and silicone sealant, the seal is highly dependent on the quality of the installation. Tournesol offers drainage adapters in standard sizes between 1/2” and 1” diameter. These units can be installed in pots, planters, and liners, and are double-gasketed for a positive, reliable seal. They are available with a “slip” connection (for gluing in PVC pipe) or a threaded female connection to use with a threaded pipe.
The “TODA” is a drainage adapter fitted with a manual ball valve. It allows the maintenance team to let the planter drain during their typical maintenance cycle and prevents drainage at other times.
Vertical drain example: Horizontal drain example:
16. What is an Overflow Drainage Adapter (ODA)?
The ODA is attached to the bottom of the container and raises the height from which the pot drains. We developed it for use with our CWM Modular Container Irrigation System. Without the use of an ODA, some of the water coming out of the CWM will drain out immediately and will be lost instead of being wicked up to be used by the plant. By using the ODA, the irrigation water is held for long enough to be absorbed by the soil. For most efficient use of the CWM system, the use of ODA is strongly recommended.
17. How many ODAs do I need?
One for each drain hole. Each CWM is typically delivered with one – if you need more, speak with your salesperson. If using more than one, they should be at the same height.
18. Why might we use an Overflow Drainage Adapter (ODA) without CWM Modular Container Irrigation?
Many projects, especially in climates that don’t get much rain, use the ODA in place of a saucer. The ODA turns the bottom of the pot into an internal saucer. It allows drain water out when it builds up, but normally doesn’t drain.
19. Can the height of the ODA be adjusted?
Refer to the illustration of the ODA assembly above. The ODA is delivered with a 6” section of ABS pipe, which would raise the drain depth to 6”. This height may be adjusted by cutting the pipe down to the desired height or increased by using a longer ABS pipe of the same diameter. The taller the overflow adapter, the more water it will “capture” in the drainage layer before discharging.
20. What prevents soil from washing out the overflow drainage adapter?
The filter fabric wrapping the pipe prevents soil from washing down the pipe. However, the drain water may still carry any staining tannins absorbed from minerals in the soil.
21. Can an ODA be used with a gravel drainage layer at the bottom of the planter?
We don’t recommend using a gravel drainage layer with an ODA and CWM irrigation system. The gravel layer does not have capillarity so water will be trapped in the gravel layer up to the height of the ODA. The water will not have a way to migrate/move up to the soil media and will remain in the gravel layer where it will either stagnate (causing the planter to release a foul odor) and/or freeze or crack due to ice expansion (depending on your location).
The planter will retain water up to the height of the ODA (see “B” in figure above), roughly 6” of excess water or the drain depth of the cut-down or extended ODA. Once the water level reaches the ODA, it flows out of the planter drain hole below. The filter fabric prevents soil from washing down the pipe (see “A” in figure above). However, the drain water will carry any staining tannins absorbed in the water.
ODA drain water example:
22. We’re using one of your container irrigation inserts - how does it drain?
Insert-style irrigation systems have an overflow drain on the side (see Figure below). When used indoors (where you don’t want the system to drain), insert the enclosed plug into the drain. For exterior, the system will automatically allow excess water out. If the unit is filled with water, the drain may be plugged – remove the insert from the pot and check. Alternatively, make sure water is draining from the decorative pot below.
Container irrigation drain example:
Steel Planter Drainage
23. Are we able to waterproof the inside of steel planters? (Example: interior application)
We can apply TourneSeal to help waterproof weathering steel planters; powder-coated planters are automatically waterproof, yet an additional layer of TourneSeal for the interior is recommended if you don’t want drain holes.
24. Can weathering steel be used for a bioretention planter?
Tournesol will want to coat the inside of the planter to prevent premature rust/corrosion on a bioretention planter. Weathering steel will still corrode and degrade if it is left constantly wet.
25. Can drain holes in steel planters be drilled in the field?
Yes, they can. Typically, the planter will be delivered with drain holes from the factory. More holes or different locations can be made in the field. Their floors are stainless steel, so drilling into the floor won’t cause rust. On weathering steel planters, neither the inside nor outside of the planter is painted and the floor/bottom is raw stainless steel, so there is no need for touch-up paint. Drilling steel in the field may take time but can be done with regular tools.
Additional Resources: Commercial Planters | Container Irrigation Products | Irrigation FAQ's | Large Metal Planters | GFRC Planters | FRP Planters