Dosing unit anti siphon question

[Raptor72]

I'm not sure if anti-siphon is what I'm referring to, but here it goes.

I have a Marine Magic dosing unit with slave unit attached. I've been having issues with the doser not working properly because the fluid in the tubing drains back down into the containers over time. When the time comes for the unit to dose the programmed amount, it doesn't reach the sump.

The picture shows how the tubing is routed. I wouldn't think that the containers would have to be above the dosing unit to alleviate this problem, so what's the answer?

[rwb500]

i've never had a peristaltic pump that allowed backflow (or any flow at all when not turned on). are you sure you're using the correct tubing inside the pump heads?

if you raise the containers a few inches there will be less pressure pulling the fluid back when the pump is off, so that might help.

[Raptor72]

Thanks for the reply. All the tubing used is the one that came with the units. I'll see if raising it , akes any difference. Three of the motors have gone out and I have ordered replacements. I would really like a better setup with something of higher quality but the choices seem slim.

[rwb500]

yeah it sounds like new dosers should be at the top of your wish list. if you do a search you can see what kind of lab-grade pumps people are buying on ebay. try searching RC for "peristaltic ebay" or "masterflex pump" or something. you can get a good double-line pump (great for 2 part) for like $50 i think.

[Raptor72]

I hear you. I'm going to replace the 3 pumps and see if it still works. I'd like to leave it as an all in one automated doser. I need to have 4 working pumps.

[kurt_n]

How many rollers are inside the head? Two? Four?

In theory, all peristaltic pumps should provide backflow prevention because there is always a roller "pinching" the tube. But with a head that uses just two rollers, depending on where the pump turns off, you might be at that point where one roller is just coming off and one is coming on - allowing fluid to pass. And if the rollers aren't located accurately, you might have one off and the other not on yet... creating a path for free flow.

With four rollers, you will never have that issue. You will always have a minimum of two rollers in contact at all times with no chance of backflow.

Many manufacturers these days seem to be cutting costs by just making pumps that use two rollers. While it may be cheaper, it doesn't do us much good for consistent results.

[Raptor72]

This doser has 3 rollers per pump

[Dapg8gt]

Have you made sure it's not letting air in around where the hose is attached to the pump? Do all the pumps do it or just one? If it's all of them I'd be willing to bet it's leaking where it's connected to the pump.

I've always ran zip ties on my peri pumps as a safeguard against this.

[Raptor72]

They're all doing it, so I'll try the zip ties. I didn't think about that even though I ve seen it before. Thanks

[Raptor72]

So I ended up replacing 3 of the motors which entailed some soldering. I then reassembled everything and zip tied the ends that connected to the motors. I could feel that the tubing fit a little loose on the connections and thats more than likely where the air was entering the lines. I'll check it in a few days and if it still looks like it's losing suction, I'll snip off the loose ends of the tubing and reattach. Thanks again for the input.

[AZRippster]

Hey Cesar!

Due to the possibility of seal leak and drainage, the only safe way to have dosing containers is below the pump. A guy who just bought one of the new Neptune DOS pumps just dosed an entire gallon of Kalk due to having his containers above the pump. Neptune uses high quality stepper motors in their system, but chose to go with only 2 rollers. If an air leak occurs anywhere in the chain between the containers and the end-point, i.e. sump, then a siphon or back-flow can happen. On mine I opted to get slightly oversized barb connectors that reduce from the metric tubing most of the imports use, to a common 1/8th Excelon tubing I use throughout the system. This allowed me to make airtight seals without the use of zip ties. The problem with zip ties is they don't crimp around the tubing evenly. There will be a point where if too much tension exists between the tie and the tubing, a small amount of tubing can lift creating an air leak. Hose clamps tighten evenly around a hose or tube, but tough to find sized for this application.

Here are a couple of shots how I have mine.

Russ

[Raptor72]

Barb connectors! I'll be on the lookout for those. Thanks for the heads up.

Your setup looks great

[zachts]

sounds like another crappy cheap dosing setup. too many of those floating around for way too inflated prices. (they are so easy to DIy for better quality) there should NEVER be back siphon on a peristaltic pump if it is set up properly it doesn't matter where your supplement containers are in relation to the tank. If it back siphons out of the box get your money back it is garbage. for what it's worth all the dossers using heads like that are cheap crap. $50 more and they could have been using high quality pump heads....but that would have cut their profit margin in half.......

[AZRippster]

Hey Cesar,

Go to ebay and do a search for:

ELDON JAMES C2-1.5 NK-QC Reducing Coupling,1/8 x 3/32 In, Kynar G6173903

These are the ones I used with my Kamoer dosing pump. Although some of what zachts says may be true, and what a ray of sunshine he is, these created a nice seal with all my lines. I actually own a Cole-Parmer Masterflex single head pump and although not absolutely necessary, they recommend having whatever is being dosed lower than the pump.

Check this out:

http://www.reefcentral.com/forums/sh....php?t=2476302

Neptune goofed by not having their heads be 3 roller, but using stepper motors is a "step" up from what we have. I'm interested in seeing if it's possible to retrofit the stepper versions into our chassis and use the interface to control them.

Good luck on getting your system back up and going.

Russ

[zachts]

Nothing wrong with a two roller pump head. They work just as well and should not back siphon as one roller is always pinching the tubing against the housing. I use several Welco pump heads in my DIY dosers. They look similar to what the DOS is using and may well be made by the same company but they are gear drive and not stepper motors, however they have enough power to run the supper long life PharMed tubing which is a huge step up from what most hobby dosers are using (silicone in most cases).

[Raptor72]

Thanks for the great input guys. I do wish that there was a great unit out there that would fill the niche. I'm not looking for a DIY project but something that is supposed to work like its supposed to. I'll check out the links and let you know if I come across anything else.

I checked out the link for the DOS doser, wow! What a shame, but at least he got a t-shirt out of it. REALLY! ? WTH! I can't even imagine what kinds of words I would have for their reps.

[zachts]

The all time hightest quality units you could get your hands on would be the Cole-Parmer Masterflex pump heads and digital drives. (ebay is a good place to find them but they are NOT Cheap! Genarally $200-$400 for a complete tested and working unit) Well worth it for critical things like Auto Water Changes or Calcium reactors, a little over kill for dosing though, but one drive could run up to 4 pump heads on most models which would let you dose solutions like two part plus mag, as long as you are ok with the +/- 3% deviation possible between heads when running three stacked on on motor (perfectly acceptable deviation IMHO) used a setup like this for a while for dosing before I switched over to my Auto Water Change, snagged it for $40 shipped and came with three heads and a hefty Pittman 24v motor that I just ran off a timer.

Sadly you'll never see CP heads in a hobby doser, they sell for upwards of $150 per head new. Plus need high torque motors in order to run PharMed or Norprene tubing (best stuff for our hobby) You'd be looking at a 3 Channel Doser with a retail price over $2,000 likely.

[tkeracer619]

Originally Posted by zachts

Sadly you'll never see CP heads in a hobby doser

Never say never . Someone creative may come up with something.

[Raptor72]

Not to beat a dead horse, but after looking in the garage, I found some connectors that are almost identical except that these have a barb on each end. They are used for the micro irrigation tubing. I'll be replacing the stock ones with these. I think that the small flat section after the barb will be perfect for a zip tie.

[AZRippster]

Oh cool, I didn't think about using irrigation barbs. I used the reducer barbs so I could use 1/8" ID Excelon RNT for most of my lines to a 3/32" for the PharMed dosing tubing my pump heads use. The tubing is actually metric, but the 3/32" is just right that they really hold the tubing without over expanding it.

Glad you found a potential solution. I'll remember that for the future.

Thanks!

[Webmanny]

I had the same issue with a brand new dosing unit. My solution was very simple. I went on eBay and got these check valves. Problem solved.