Metering pump challenge

**Treeman** · 06-26-2010, 09:32 AM

I am installing a peristaltic metering pump in our greenhouse water system with a chemical to reduce scale build up. The proportional pump system will get a signal from a water meter for every quart that passes by, and a dose of juice will go in to a 3/4" line which then tees off about 4 feet away. Flow can be less than 1 gpm up to 20gpm. Mix rate is around 1:5,000.

I am concerned that the fluid won't be completely mixed before teeing off to go to different places. The company says it should work.

Can someone explain how this mixing works. I considered a static mixer or some kind of "mix chamber", but they said it was not needed. Doesn't water flow kind of "laminaer" in pipes without any mixing?

Thank you.

**Gary Slusser** · 06-27-2010, 08:09 AM

When they say "it should work", it seems to say they aren't sure. I'd add the inline mixer.

**Akpsdvan** · 06-27-2010, 11:08 AM

You need contact time, be it an in-line mixer or a media tank with nothing in it for contact time.

Say a old Sears tank 10x40 with an in out head on top and the just injected water going in and down the center or disturber tube and then up through what would have been media but there is no media just the water and then into the out going line.

**Treeman** · 06-27-2010, 12:07 PM

Thank you for the responses. I am familiar with the chlorine systems that require a retention tank that allows time for the chemical to do its job. I am injecting a unique mild acid that * "supposedly" changes the water into non-scale forming, so I just need good mixing between the injection point and the tees a few feet away (no pressure tank in my set up). * "Supposedly" means that this is a trial and might turn out to be snake oil.
TYPICAL CHLORINE SET UP:

By "old Sears tank" are you referring to an old water softener tank (sans media)? That seems like a good idea.

What about fabricating a "labyrinth" of larger 2" pvc .....multiple S shape to allow the fluid to mix?

Is there a way to PM/private message my layout to you guys for assistance? Thanks for the input.

**Akpsdvan** · 06-27-2010, 03:45 PM

I have windows live and am on some other diy sites... same handle

what if you as to inject the fluid and then go from say 1" to 4" and that 4" was to run up say 6' and then go back down to the 1" and do where needed?

**Gary Slusser** · 06-27-2010, 10:07 PM

An acid will dissolve scale but IMO will not prevent scale from forming, it will simply lower the pH.

My initial guess was that the chemical was polyphosphate, a sequestering agent. IIRC you don't not need retention for that, just having the two fluids mixed well is all that's needed and a static mixer will do that better than any amount of retention.