adding a liquid to a hosepipe

[Janice]

Hi I'm not sure if I can explain this properly but here goes.

I want to add a liquid fertilizer to my automatic watering system in my greenhouse which is fed by a Gardena electronic timer. Basically I want to convert the whole system to hydroponics but I need a way to add the nutrient to the water flowing in the hosepipe without the nutrient running out when the water is stopped.

What I need is for a tank of nutrient to be mixed in with the water but not for the water to flow through the tank and mix it all in at once so that I can leave the whole thing for a couple of weeks when I go on holiday so that everytime the water flows a measured amount of nutrient is added to the water.

Is such a thing possible or will I have to get a pump and a large tank and pump the water and nutrient around in a closed system? The problem with that is if the pump fails the tomatoes die. This is all for next year as I want to try a different method of growing tomatoes so that it is all automated and I want to try to grow things hydroponically and not have to rely upon unreliable neighbours.

Hope you understand all this

Thanks Jan

[Mj]

[The Medway Handyman]

Venturi based systems are available. No knowledge of this application, but when I worked in the cleaning machine industry we used a very simple metering system.

The chemical (in your case nutrient) was added to the water flowing into the bucket/machine tank by the flow of water. Dilution remained the same regardless of water pressure or flow. No moving parts, dilution ratio was set by using one of a number of colour coded metering tips supplied with the kit.

Sorry, can't recall makers name at the moment.

[meow2222]

this sort of kit has been common in commercial nurseries for decades. ISTR a Cameron diluter. Probably available in plastic for home use by now.

They were deemed a safety risk due to back syphonage, so ensure a double check valve is used with one.

NT

[Owain]

Is this the same way that cleaning stuff is added to pressure washers? It might be possible to cannibalise a pressure washer lance forthe dilution mechanism

Owain

[The Medway Handyman]

More or less yes. The venturi would be machined into the pump head, the lance just allows a choice of 'same pressure as nozzle in venturi' (therefore no chemical) or 'lower pressure than nozzle in venturi' (chemical).

[The Medway Handyman]

The water authorities consider everything to be a safety risk due to back syphonage. Some don't consider a NWC approved double check valve sufficient protection.

[fred]

In article , Janice writes

Try:

hanging basket version might suit you. Watch out as the others are designed for higher flows and just won't lift the feed if you run them at low flows. They do a 10% introductory discount.

Note however that they don't seem to be advised for long slow delivery, the notes on that page suggest a short feed cycle then water alone then refill and feed again.

are the makers who do sell as well but may not always have stock, useful info on site.