Assembly Gardena drainage valve

Assembly Gardena drainage valve

When it comes to the winter months, it is important to drain the irrigation system. That means it has to be winterized and the water pipeline has to be de-watered. There are two options for this. First, you can de-water the pipeline with compressed air or, secondly, use a drainage valve . Therefore plan and install it in your water pipeline. Since I do not have a compressor, I decided to use the Gardena drainage valve. Thus, I have assembly Gardena drainage valve in each irrigation strand at the lowest point of the water pipeline.

For this purpose, Gardena provides a solution consisting of the following components:

  • Gardena T-piece 25 mm x 3/4″ female thread (Art.-No .: 2790-U)
  • Gardena drainage valve (Art. No .: Drain Valve)

For the installation of the drainage valve at the pipe end, use the connector (item no: 2761-20).

Operation of the Gardena drainage valve

Gardena’s drain valve opens when there is no more pressure in the line. Thus, one can separate the water pipeline from the water source in late autumn and automatically opens the valve and the remaining water can escape from the line. It is therefore no time-consuming blowing out of the water pipe with air pressure. In irrigation line, a drain valve is installed. Install the valve at the lowest point of the pipeline. If the pipeline pressure drops below 0.2 bar, the water can flow out. Therefore place the valve in gravel. Install the drain valve face downwards in a gravel packing of 20 x 20 x 20 cm of wash coarse gravel (min 8 mm Ø).

To check the function of the drain valve, it can be installed in the valve shaft. For this purpose, different products are offered on the market such NDS 111BC Standard Series Round Valve Box with removable ceiling

You can find more information about my automatic garden irrigation with products from Gardena, Hunter and Homematic in my blog.

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Garden irrigation with Hunter or Gardena

I have been operating my garden irrigation for several years now and it has done an excellent job in the great summer of 2018.

In my garden irrigation I use the products of Hunter and Gardena. In this blog I would like to explain the reasons for my product decision. These are my own experiences and opinions.

Sprinkler – Hunter or Gardena

Deciding for my opinion were our holidays in Florida. All the houses have garden irrigation systems that irrigate the large gardens every night. Very precisely, the pop-up sprinklers have done their job and irrigated the intended area. Predominantly Hunter products were installed there. In various discussions with homeowners, the longevity and low maintenance of the sprinklers has become clear. Even after years of daily use, the sprinklers perform their work precisely and also the spring pressure in the riser of the transmission controller does not diminish. I can also confirm this with my use for several years (no daily use, but very frequent in summer) in the garden.

Based on the experiences from Florida, I decided for the sprinklers from Hunter. I have seen the Gardena sprinkler in the handyman market and read a variety of forum posts about them. Finally, I preferred the Hunter sprinkler product quality.

In addition, I was convinced by the great radius of the Hunter sprinklers and the various spray nozzles for the close range (MP Rotator, Pro-Spray nozzles with fixed sector, adjustable nozzles, special nozzles).

Water Pipeline – Hunter or Gardena

Gardena Pipeline

After the decision of the sprinklers had fallen, I now needed to decide which water pipeline I want to use. There is a big difference to the situation in Florida. In Germany, winter temperatures reach minus degrees and the water freezes in the water pipeline. Thus, drainage is an important issue to protect the pipeline from damage. If you deal with the Hunter water pipeline, you quickly get to the area “blow-out method” when draining. Since I do not have an air compressor, this method was not suitable for me.

The second possibility of drainage via manual valves, which are installed at the lowest point, was the solution for me. Gardena offers an automatic valve for drainage. In the event of a pressure drop in the pipeline below 0.2 bar, the valve opens automatically. In other words, in preparation for the winter, I can disconnect the water supply in the garage from the pipeline and the existing pressure drops. Thus, the water can flow through the Gardena drainage valve into the soil. This has not resulted in any damage to my water pipeline in the last four winters.

Magnetic valve – Hunter or Gardena


Magnetic valves are required to control the individual pipeline path. Both manufacturers offer systems with 24V AC voltage. Also, the valves of both manufacturers can be disassembled and repaired if necessary. Spare parts can be ordered individually on the internet. In addition, both manufacturers offer a manual opening of the valves to manually activate irrigation. If you do not use the solenoid valves in a building, like a garage or basement, you need appropriate valve boxes to put the valves into the ground.

For my irrigation solution, I have chosen the Hunter PGV-101G, because these valves are cheaper priced.

Planning Tool – Hunter or Gardena

Garden irrigation planning

Another reason for using the Gardena Pipeline has been Gardena’s planning tool. The company Hunter provides only a planning manual. With the Gardena planning tool you get a good planning blueprint as well as a list of the required material. I have ordered the corresponding material for the pipeline from Amazon. But int the end the implementation was different than planned. I needed additional connectors (especially L-pieces) that I could buy at short notice in my well-stocked hardware store. But even with those unplanned circumstances, I still managed to install the whole system in one day of work.

You can also find information about planning your project in my blog.

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Checklist for automatic garden irrigation

Garden irrigation planning

To reach a well thought out automatic garden irrigation, start with the planning phase. You should be aware of all conditions before the construction of an automatic garden irrigation system. To plan your automatic garden irrigation perfectly, you will find here a step by step guide and the checklist for automatic garden irrigation.

Draw a plan of the garden

To create a plan you need some tools. In addition to pencil and eraser, you need a ruler. For the drawing of the scale plan, use a scale of 1:100 or 1:50.

Start with measuring the garden, for this we use a measuring tape. Best start with the boundaries of the property and draw it on your sheet. To use the sheet optimally, start with the longest side and set the scale. If you can divide the garden into several areas, use separate pages to record the individual areas.

After capturing the garden outlines , draw in all the surfaces that you want to irrigate. Then mark these areas as lawns, flowerbeds, shrubs and trees. In addition, mark the areas house, garage, terrace, paths and ponds that should not be irrigated.

Furthermore draw the water source (faucet or garden pump) on your plan. For further planning you need the parameters water pressure (bar) and water flow (l/h). Please look at the following blog entry: Parameters for garden irrigation.

Draw the watering plan

For your garden, there are three different types of irrigation from Hunter to choose from – Rotary sprinkler, MP Rotator with spray nozzles and micro irrigation.

In order to decide which type of sprinkler should be used where, one can use the following rule: use Hunter Rotators for surfaces larger than 5m radius, Hunter MP Rotators for surfaces up to 5m and micro irrigation for direct root irrigation.

Now, if you look at the plan of the garden, you can define several different irrigation circuits. One can make a very differentiated consideration, which also gives a complex garden irrigation solution, or you can be a little more generous. I would like to refer again to my solution under The project. As describe, in my backyard two Hunter Rotators are active to watering the lawns, flowers and shrubs. This could have been improved with spray nozzles or micro irrigation, but after 4 summers this has proven to be sufficient. In order to not irrigate all surfaces in the front yard, I used MP Rotator with spray nozzles.

Sprinkler position

If you have marked the areas for irrigation and drawn the position of the sprinklers, you get the irrigation lines. Please note the following points regarding the number of irrigation lines:

  • use of number of sprinklers. The parameter water flow is to consider.
  • Number of separate garden areas available.
  • For each irrigation line use similar sprinkler models. No combination of sprinkler and micro irrigation

When calculating the sprinklers please read the following blog entry: Calculation Sprinkler.

If there are several irrigation lines during your planning, everyone receives a irrigation valve. The Homematic home automation system allows each irrigation line to switch on for different periods of time, since different sprinkler models also supply different amounts of water per hour.

Hunter sprinkler position Draw circles around the sprinklers for irrigation. The radius correspond to the range of the sprinkler used. They can realize a watering area of 0 and 360 degrees. The radius of a sprinkler must reach another sprinkler header. The garden area must therefore be covered twice. For each sprinkler different nozzles are available to adjust the casting distances later. It is advisable to take this into account when planning.

Select the sprinklers

Now you have to choose the perfect sprinklers for your automatic irrigation. Measure the radius from your plan and convert them to the real measure with the help of your chosen scale. Now you have the radius of your future sprinkler. For small radius up to 5 meters use Hunter MP Rotator, for larger distances Hunter Rotator.

The throwing distance is not only dependent on the sprinkler model, but can also adjust with different nozzles. But it is always easier to shorten the distance than to increase. Also, the flow rate of water and the water pressure influence the throw lengths of sprinklers. Hunter provides tables with the characteristics and the nozzle on their website for each sprinkler.

With the information collected, you can now check the number of irrigation lines, as described in the blog entry: Calculation sprinkler.

Planning water pipeline

For the construction of the water pipeline, I recommend you to use the Gardena Quick & Easy solution. Since you have calculated the number of irrigation lines, now at the water connection (faucet or garden pump) an appropriate distribution must be provided. To control each irrigation line separately, a Hunter valve is necessary to implement. For each valve, a Homematic wireless switch and a connection to the DIN rail power supply units must be provided.

There are several ways to install these solenoid valves. On one hand, the solenoid valves can be mounted on the house or garage wall or you can use a device to install the valves underground, flush with the garden surface. It does not really matter how you do this, but the important thing is that you install the solenoid valves locally together and easily accessible. This is important for possible maintenance or future enhancements. Please note that distances and specifications for the electrical installation are observed during the course of the 220V cabling and the water pipes.

Furthermore, draw the water pipeline for the individual irrigation lines. Each of these lines must have a drain valve. In my blog Setup I’ve shown the existing Gardena pipeline elements that can be used. In the interplay of the Gardena Pipeline and the Hunter Sprinkler, the connection cross-sections must be observed. There are the variants ½ inch or 3/4 inch. In each irrigation lines, a Gardena drainage valve should be provided. This gives you the option of de-watering the water pipeline and protecting it from frost damage during the winter.

Shopping Garden irrigation parts

Now that the planning is complete, put yourself now a shopping list along with the necessary parts. I bought garden irrigation on Amazon.

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