http://cr4.globalspec.com/thread/12143/Peristaltic-Pumps

Where are you...peristaltic or gravity is the best way forward.

Chemical controls do 'em.. it's where I work.

Maybe a small header tank with a small bore outlet T'd into the water flow (double check valve in the water line before your injection point, some sort of valve to limit the flow... rely on gravity/venturi action.

Del,

Seattle area. This is a marine head/rv holding tank treatment.

The venturi idea seemed logical but I wasn't able to work out the metering. It would be ideal since the dosing would be dependent on use and it would be passive and cheaper to produce. Often there will be periods with no use when additional chemical injection isn't required. A header tank of 1 liter would be about the maximum. Thanks.

The metering...

Just about anything! A rubber tube with an adjustable screw clamp... something like a hospital drip..

To measure the delivery... watch how quick the header tank goes down..(use a tall thin tank so you can measure it..then swap to a bigger tank for real use, & then monitor the level over each day) If you need accuracy..buy a peristaltic. (you don't even need much of a control system... a variable DC supply will do fine for low doses on a DC motor peristaltic. (We don't have a US agent... else I'd sort something out for you... at special CR4 rate )

Del

An infusion pump sounds your best and cheapest method...

Just have a disposable syringe driven by a small geared motor to dispense the required volume per minute etc...

Very easy and used in hospitals all over the world...

John.

We need more info.

1ml per cycle is meaningless if we don't know the cycle time..number of cycles per day...is this going 24/7.

Electroman's syringe is fine for relatively low number of cycles ..but if there is one cycle every 10mins 24/7...... maybe need something with a bigger reservoir.

Del

Sounds like you're trying to create a commercial product. Here's some food for thought. Gravity feed a normally closed 12 VDC solenoid valve with your oil. Install a paddle switch in the holding tank in such a location that the flush water will strike the paddle. Run the wires from the paddle switch out of the tank through some sort of compression gland. A capacitor is connected to the solenoid valve coil through the paddle switch. A resistor is used in the supply line to limit the current flow to the capacitor. Here's how it works: When the head is flushed, water flows into the holding tank. This water flow trips the paddle switch. The paddle switch completes the circuit from the capacitor to the solenoid. The stored energy in the capacitor opens the solenoid valve allowing the oil to flow (by gravity) into the holding tank. The capacitor's energy is quickly used up so the the solenoid valve closes shutting off the flow of oil. You size the capacitor relative to the time needed to dose the tank, and you size the resistor to avoid holding the solenoid valve open. When the water flow stops, the switch opens and the capacitor starts charging for the next cycle. Plastic solenoid valves are available from a number of sources as are cheap flow (paddle) switches. Hope this might help to trigger your imagination.

Autochlorinators are used in potable water applications. An autochlorinator is a passively-operated device that feeds a predetermined ratio of liquid, in this particular case either sodium- or calcium-hypochlorite solution, into the flowing water stream.

Here's the principle of operation. The stream is passed through an orifice plate, and the high and low pressure tappings at the orifice are used to provide the driving force for a chemical dosing bottle with two connections, with a diaphragm to separate the injection liquid from the driving liquid. As the flow increases, the driving force increases, and the flow is dosed with a greater quantity of liquid, though in the same proportion as compared to before the flow increased.

Something simple like that, perhaps?

You may try using the following pump:

http://www.tomopal.com/product/product_detail.aspx?pid=1602&lvl0=0&lvl1=0

The KDS 100 is an effective syringe pump designed to hold a single glass or plastic syringe, of any make, from 10 microliter to 60 milliliter. Dispense Volume Mode: The pump keeps track of volume dispensed and automatically stops when target volume is reached. Run Mode: Pump runs at the set flow rate until stopped manually.