Simple Doser

pterfloth · #1 04-06-2009, 12:09 AM

I have been working for several days on an inexpensive but reliable means of dosing 2-part and other additives. After several attempts I have come up with this design. It has been running for a couple of days now and seems to work quite well.

Parts Required:
Airline
Check valves
Airline "T"
Airline pinch valve
Timer
Air pump
Additive reservoir

The premise of the design is that a given length of airline will contain a given amount of liquid, which can be pushed out of the airline by an air pump. If the airline is cut to the appropriate length, the desired volume will be delivered. By using a siphon to refill the airline and a timer to periodically pump out the liquid in the airline, a dosing scheme can be acheived.

The design is shown below:

Once a siphon is created out of the reservoir, the coil of airline will fill up with liquid until it reaches the height of the liquid in the reservoir. When the air pump is turned on by the timer, the liquid in the coil will be pushed into the sump. The pinch valve creates some backpressure to prevent liquid from siphoning out of the reservoir once the airline has been purged and only air is flowing through the line. This is important if you are using a 15 minute increment timer. The top of the discharge line must be above the height of the liquid in the reservoir to prevent continuous siphoning.

So far I have been able to achieve delivery volumes of 5, 10 and 20 ml of liquid per cycle.

Snaz · #2 04-06-2009, 12:14 AM

Looks nifty but what happens when the airline builds up crud or is warped out of shape by any number of reasons? I would think the volume of the measured length would change.

hillegom · #3 04-06-2009, 12:19 AM

I like this, very innovative.
Simple and cheap.

pterfloth · #4 04-06-2009, 12:41 AM

Quote:

Originally Posted by Snaz

Looks nifty but what happens when the airline builds up crud or is warped out of shape by any number of reasons? I would think the volume of the measured length would change.

I'll let you know how it turns out in the long run. I'm primarily going to use this for DIY calcium and alkalinity additives. I don't get any precipitates in my mixing containers. I used rigid airline for the stems in the reservoirs. I don't think the coil will change much in shape. But we'll see.

GreenSpottedPuffer · #5 04-06-2009, 02:49 AM

What about when dosing changes?

Only reason I ask is that now my tank has really started to grow and the dose of two part seems to change every week or two.

pterfloth · #6 04-06-2009, 02:59 AM

Quote:

Originally Posted by GreenSpottedPuffer

What about when dosing changes?

Only reason I ask is that now my tank has really started to grow and the dose of two part seems to change every week or two.

My dosing is pretty constant right now at 100 ml/day each of Randy's recipe for calcium and alkalinity. I am using 10 ml/feed cycle or 10 cycles per day. If I have to increase or decrease it, I'll just change the timer settings for now. That would be the same if I had a peristaltic set-up, which I would love to have but can't justify at the moment.

BTW, I love your tank!

Frenchie · #7 04-06-2009, 03:00 AM

Looks interesting. Much cheaper than dosing pumps. Im gonna tag along and see how it turns out.

GreenSpottedPuffer · #8 04-06-2009, 03:40 AM

Quote:

Originally Posted by pterfloth

My dosing is pretty constant right now at 100 ml/day each of Randy's recipe for calcium and alkalinity. I am using 10 ml/feed cycle or 10 cycles per day. If I have to increase or decrease it, I'll just change the timer settings for now. That would be the same if I had a peristaltic set-up, which I would love to have but can't justify at the moment.

BTW, I love your tank!

Thanks!

Ok, makes sense. I was just curious about how hard changing doses might be. I am about to buy the dosing pump off of Bulk Reef Supply and just thought I might think about this...

But to be honest, its easier for me to just grab the BRS dosing pump (about $100CAD). Its still much cheaper than what I was going to pay for a Ca Reactor.

Looks great though! If I had more patience, I would probably set this up for my tank

pterfloth · #9 04-20-2009, 05:27 PM

Just to provide an update. Been running for over 2 weeks now. Very happy with results. I highly recommend digital timers with 1 minute increments and Fusion type check valves (the ones with the little ball inside). The spring-loaded check valves didn't work for me.

Dosing has proven to be very consistent, eliminating the daily chore of adding 2 part and the large swings in water parameters it produces.