How To Build A Greenhouse Rainwater Catchment System?

Collecting rainwater from the greenhouse structure is not only an economical way to water plants but also very beneficial. There are many reasons why rainwater is better than tap water for plants apart from it being environmentally friendly. Today I will show you how to build a greenhouse rainwater catchment system so you can collect the water from the greenhouse when it is raining.

How does greenhouse rainwater collection system work?

It works by catching rainwater from the greenhouse roof into the gutters on each side of the structure. The water then drains into the downspouts which are connected to PVC pipes. These pipes take the water to the water barrels where the rainwater is stored.

How to build a greenhouse water catchment system?

How easy the installation of water collecting system is depends on your existing greenhouse. If your greenhouse already comes with the rain gutters, for example, as Palram Hobby Greenhouse model, then you need just need to connect them to water barrels.

I would recommend installing two barrels, so it is one on each side to maximize amount of rainwater you can catch. Here are the steps to follow when installing water system on existing greenhouse guttering:

• Measure the length of the gutter and find a suitable gutter outlet.
• Push in the gutter outlet into the gutter and fix it in place with silicone sealant.
• Attach a 90 degree pipe bend to drain the water away from the greenhouse structure. You can skip these steps by getting a greenhouse rainwater kit which comes with
• Connect downspout to the bend and attach it to the water barrel. Alternatively, you can skip 3 steps above and get a greenhouse rainwater kit which comes with downspout, end cap and fittings. It fits the majority of greenhouse models and slots easily into gutter end.
• Choose a water barrel with lid and mesh filter so the leaves and pests don’t get in the rainwater.
• Place the water barrel on the concrete block or water barrel stand. That way you will have room for buckets, pails and watering cans to fit under the spigot. Moreover, it will ensure that water flows at a faster rate and drains completely so water is not going to be standing. Water barrel stand will also help to keep a water barrel in place by supporting it whilst minimizing bowing and bulging.

How to attach guttering to a greenhouse?

Step 1 – Measure the length of the greenhouse just under the roof where you are going to install gutters.

Step 2 – Make sure to choose the gutter which has the filter to prevent leaves and debris from getting into the water. Alternatively, you can purchase gutter guard mesh and install it on gutter yourself.

Step 3 – Take a drill and put on 1/2-inch gutter saw. Drill 2 inches from the end of the gutter and pop in the outlet for the downspout.

Step 4 – Screw the gutter brackets to the greenhouse frame at the equal intervals, position each bracket slightly lower on the frame than the previous towards the downspout. When you put the gutter, it will be slightly sloped, it ensures that rainwater is going to flow.

Step 5 – Sit the gutter on the brackets. If you are joining two gutters, use linking brackets which you need to secure to the gutter with silicone sealant.

Step 6 – Attach the downspout to the outlet. Flexible construction is easy to customize.

Step 7 – Connect the downspout to a water barrel.

Step 8 – Place a water barrel on a concrete block or a water barrel stand.

What is the best rainwater tank for garden use?

The best rainwater tank should hold at least 40 gallons of water, designed for long-term usage and withstand both hot and cold temperatures. It should not be cracking, splitting or leaking.

Most of the commercially available barrels come with the cut out for the residential downspout, if you go for this option you just need to fit the connected to guttering downspout into the water tank.

Here is a good option with a flat back design so you can put it right up against greenhouse structure so you don’t need to buy pipe bend and additional pipe to link the downspout to a water tank. Also, it has a front side overflow, so, when the tank is full, water will be directed away from the greenhouse structure.

Moreover, you can connect multiple barrels to harvest more rainwater via side overflow with linking kit.

The tank can hold up to 50 gallons of rainwater and it comes with the plastic screen mesh on the top to keep out pests, animals and debris. It is easy to remove and clean.

What is the best material for a water tank?

Polyethylene account for the best water tank material and most of the models are made from polyethylene resin. It is BPA free, UV resistant and doesn’t rust, rot or mold. Polyethylene is strong meaning that rain barrel can take heavy impacts and will withstand harsh winters. It is durable and crack-free.

If you want to purchase a cheaper option but of the quality, you can opt for this model which is only 30$ for a 66 gallon rain barrel. I like it because it is portable so you can move it as required or fold it and store in your garage when not in use. Rain barrel is made of PVC frame and anti-corrosion PVC mesh fabric. The structure of PVC is similar to polyethylene meaning that it is very durable.

How big of a rainwater tank do I need?

If you are planning to collect rainwater from greenhouse structure only, 50 gallon rain barrels from both sides of the structure should be sufficient. How big of a rainwater tank do you need depends of the size of your greenhouse, whether you have enough space in your garden and on the amount of rain you get in your area.

How much does a greenhouse rainwater harvesting system cost?

Although the initial installation costs might be a little bit high, you will get your money back quickly and significantly reduce your water bills after installing rainwater harvesting system. Moreover, rainwater is better than tap water for plants.

So, how much does it cost to build a greenhouse rainwater harvesting system?

On the average, the cost of a rainwater collecting system for a 6′ x 8′ greenhouse is around 160 – 313$ not including the labor. It takes approximately 2 hours to build a greenhouse water catchment system. Here is a breakdown of the materials used along with the prices:

Water catchment system can be easily connected to the greenhouse irrigation system. It will ensure that your water tank is not going to overflow and if it is not raining, you can always disconnect it from the tank and link to another water supply.