H2O DJ - Inline Water Mixer /Foam Lance/Fertilizer

The H2O DJ allows you to attach a common PET bottle of any size to your garden hose and adds small amounts of it's content to the bypassing water stream. The amount that is added can be linearly adjusted by turning the valve-cap and ranges from closed (nothing is added, pure water bypasses) to about 0.5 litres per minute of additive mixed into the water.

Applications:

• Turn every water sprayer or power washer into a foam lance to clean your car or terrace. Just fill liquid soap or detergent into the bottle and when you are done: just close the valve-cap to rinse it down with fresh water.
• If your dog allows it, put some dog shampoo into the bottle and give it's paws a quick rinse after a muddy walk. (please be careful with the water temperature of sun-exposed hoses!)
• Fertilize big areas of your garden or potted outdoor plants in one go! A 1:10 ratio of fertilizer to water (e.g.) attached in a 1 litre bottle will give you several minutes to spread the fertilizer evenly.
• You can use it in a similar way to spread all kinds of beneficial bacteria or cultures in a larger area around your garden. This technique of “inoculation” can help your garden in many ways. There is an interesting symbiosis between nitrogen-fixing bacteria and legumes that can be kickstarted, mycorrhiza spores (fungi) can be spread to help the roots absorb nutrients and effective microorganisms (EM) can be brought out easily.

This print requires 4 O-rings type “R9” with 11.2 mm inner diameter and 2.5 mm thickness. You might have them at home already, otherwise they can be sourced from about every hardware store.

Additionally, you will need a flexible tube with 4 mm inner diameter that needs to be cut to the size of the PET bottle you are using and reach all the way down. Basically everything works that you can manage to fit onto the attachment point but it has been designed with these “micro-dripper” system tubes in mind that are widely used in irrigation systems. (4mm inner/ 6mm outer diameter)

Alternatively the tube and O-rings can be printed in TPU using the provided print profile. They do their job well, although the O-rings need to print very clean to ensure a waterproof seal and might need a small manual clean-up. The tube is 34 cm in length and maxes out the buildplate of a P1/X1/A1 printer but could be scaled down in the slicer to the perfect size.

Assembly and Functionality:

The H2O DJ consists of 2 parts. The main body has 2 common hose quick connectors on both sides. Slide one R9 O-ring each into the first groove on those connectors like shown in the picture. The valve-cap (2nd printed part) requires 2 R9 O-rings as well, that need to be fitted into the 2 grooves at the top of the part.

Screw the valve-cap into the main body carefully and watch out to not have a ring slip out in the process. The valve should screw in with some - but not an inadequate amount of - force. A tiny amount of lubricant could help but shouldn't be nessecary.

Pick a bottle any size you want with a PET - thread and cut the tube that you are using roughly 2 cm shorter than the bottle. Attach this tube to the small inlet at the bottom of the mixer, insert the pipe into the bottle and screw it on. The PET-connection can be tricky at times to get waterproof depending on the manufacturer but an addition O-ring behind the thread on the bottle or some PTFE (teflon) -tape will solve that problem easily, should it occur.

Connect your garden hose and sprayer attachment to the H2O DJ. The arrows on both sides of the part indicate the intended direction of waterflow. When the valve is closed completely, only fresh water should be flowing by and no mixing should occur. When turning the valve-cap in “+” - direction, the lower O-ring slides over a slit on the inside of the part to gradually open up a small water channel that allows the content of the bottle to mix with the bypassing water. To achieve this, the outlet utilizes Bernoulli's principle to create negative pressure inside the suction tube. The bottle fills with clear water through a connection into the main water stream at the opposite side of the part. The inlet is heart-shaped (because why not ;) and continues to redirect the water internally a few times to slow it down. This is done to prevent the mixing of liquids (e.g. soap and water) inside of the attached bottle and allows for an even ratio of additive throughout the application. You should be able to see a clear division between the level of additive at the bottom (slowly going down) and the clear water on top of the bottle.

Additionally, there is a printable Wall and Belt Mount available. It is not permanently attached to the wall, but simply hung there using 2 screws or preferably L-shaped hooks and is designed this way to be easily taken off and attached to your belt. If you intend on using the mixer stationary for your irrigation system, the wall mount can be used to keep the bottle in upright position as well.

Update 01.06.25: Added a version of the H2O DJ with an attached shower-spray-head on the output side. It is designed for high throughput and pressure and can spray about 10 meters at a slight angle. It is equally fit to clean your car with soap or fertilize your garden but losing the output sided quick connector, this fixed spray head rules out some other use-cases of course (e.g. you can't attach it to a power washer or use it as inline fertilizer addon in your irrigation system). There is a print profile for AMS and one without (markings cut out).

If you have problems sourcing the hose quick connectors, you can print them with this design here.

Like always, reach out to me should you have any problems with the design or would like to see a feature added! Happy printing and may the filament forever fall in your favor. Cheers,

fmod ;)