Considering DIY peristaltic pump, where to inject?

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A

a34536

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May 30, 2011
38
Dorset, UK
I switched from pucks to 11% bleach 2 weeks ago, and so far so good.

Now I'd like to automate the injection of chlorine. Ebay has peristaltic pumps for < £30 and the control and timing of them won't be a problem.

I think I need to inject the chlorine after the pool pump, filter, and heater, and into the return line. The pressure at this point is probably < 10psi. To do this I need a fitting to inject into the 1.5" ABS pool piping and a non-return valve.

Can anyone suggest a suitable fitting?

Anything else I need to consider?

Thanks!
 
Right, the UCINJCE has arrived - thanks for the pointer BR.

1st issue is that the thread does not go all the way up the shaft so drilling and tapping a normal 1.5" pipe will not work. I was thinking of drilling and tapping into a coupler like this one http://www.1st-direct.com/1-534;-abs-pl ... etails.htm as this gives more thickness to work with. Any view on whether this will be ok, or whether I should just get a saddle clamp?

2nd, I was thinking of using a pump similar to this, http://www.aspenpumps.com/en/standard.html as they are fairly cheap on ebay. I now have some 6mm PTFE tubing for the chemical, however now it has arrived I've realised it is quite rigid. I am unclear whether the pumps have their own internal tubing which then connects to inlet and outlet lengths of tubing, or whether I would provide a single length of my ptfe tubing which would then thread through the pump. If the latter, would this tube be suitable for this pump?

[attachment=0:15d4sf35]IMG-20110823-00067.jpg[/attachment:15d4sf35]
 
You actually can drill and tap the PVC pipe. That's how mine is done. If you want to use the coupling you certainly can.

The PTFE tubing you have will work fine. The pump will come with a pump tube that your tubing will attach to.
 
Quick update. I didn't have to drill and tap anything as the injector valve actually fitted into one of the two 1/4" screw threads on the multiport valve which normally take pressure gauges.

The Aspen peristaltic pump unit-normally used to drain condensate from AC units works well, but needed a slight modification to run continuously whenever power is applied.

I have tested the setup and it supplies 100ml fluid each minute of operation.

The pipe and fittings on the pump are 6mm ID and my PTFE pipe is 4mm ID. I am trying to find some stainless or suitable plastic adaptors to convert between these sizes. The only ones I have found so far are brass and are therefore corroding.

Anyone found anything suitable and available to the UK?
 

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a34536 said:
1st issue is that the thread does not go all the way up the shaft so drilling and tapping a normal 1.5" pipe will not work. I was thinking of drilling and tapping into a coupler like this one http://www.1st-direct.com/1-534;-abs-pl ... etails.htm as this gives more thickness to work with. Any view on whether this will be ok, or whether I should just get a saddle clamp?

*******
Quick update. I didn't have to drill and tap anything as the injector valve actually fitted into one of the two 1/4" screw threads on the multiport valve which normally take pressure gauges.
Click to expand...

I installed a Stenner injection pump a few weeks ago. I'm no expert, but everything I read in prep for installing mine suggested injecting after all of your equipment to prevent exposing them to a higher concentrate of bleach. I would guess that by injecting into the multiport, you are still upstream from at least your heater, and maybe more.

My check valve was just like you pictured. You can still drill and tap pvc even though the check valve threads don't go all the way to the end if you want to relocate it further down stream. I think the non-threaded extension is to inject more towards the center of the pipe for better/faster blending, which I don't think is needed in pool applications, and you can simply cut that extension to any desired length if it is too long. I cut my extension completely off so that I could screw it into a schedule 80 plastic elbow to make my check valve lay parallel and close to the pvc pipe. I didn't want my check valve sticking out where it could easily get bumped by accident and possibly broken off, and mounted it somewhat on the bottom of the pipe so that the pipe would provide some protection as well. Here is a picture of my install:
5ab94e88ad3518ec4bfbddcef728391c65b558d061b49375b629cfc65985b4566g.jpg

Sorry, but I don't know of any source for the hose adapters you are looking for either.
 
Yes, by injecting into the multiport I am upstream of the heater, and possibly the sand filter and I may change it at some point. My gut feel is that the slow feed rate of 0.1L per minute for a couple of minutes shouldn't cause problems. Happy to be corrected.

Nice job on the 90 deg elbow.
 
a34536 said:
Yes, by injecting into the multiport I am upstream of the heater, and possibly the sand filter and I may change it at some point. My gut feel is that the slow feed rate of 0.1L per minute for a couple of minutes shouldn't cause problems. Happy to be corrected.
Click to expand...

Honestly, I was thinking the same thing when I did mine, even though I ended up taping the return downstream of everything. I have a puck feeder installed and a check valve between it and the heater, so there is no chance of getting super chlorinated water into the heater. I suppose the only danger might be if the chlorine pump happens to run for a while when the pool pump is off. Mine is protected by the computer so no chance of that happening either.
 
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