Time to replace DOS head?

Huff747 · Aug 20, 2019

I think my issue is perhaps that head(s) are wearing out but thought I'd try and get some confirmation. Tried a search but wasn't finding what I was looking for.

I use DOS for auto water changes and I noticed my salinity was going up. I was looking over the heads and running them manually and one of the heads seems to be getting air bubbles in the line at the head. I can see a full tube of water going into the head and then air bubbles in the line when coming out of the head. And when I stop manually priming I can see that the water falls back down the line.

So should I replace the head? I checked that the connections were tight. If I'm replacing one head should I replace both?

Thanks.

Foothill Corals · Aug 20, 2019

Is there is a hole in the tubing at the head?

Huff747 · Aug 20, 2019

I pulled the head off this morning and I couldn't see any obvious holes.

ca1ore · Aug 20, 2019

sounds like you just need to replace the peri tubing

Huff747 · Aug 20, 2019

ca1ore said:
sounds like you just need to replace the peri tubing

Is that an option? (as you can tell I'm very well versed in DOS head maintenance). Thought I had to replace the entire head.

ca1ore · Aug 20, 2019

You can definitely replace just the tubing. I buy it in bulk and replace every 6 months. I've yet to replace the roller head after 18 months. Imagine you can probably get the tubing from places like BRS too.

1/8" ID x 1/4" OD x 1/16" Wall PharMed® Tubing | U.S. Plastic Corp.

Ideal for fermentation, synthesis, separation, purification, control systems, process monitoring, and protecting sensitive cell cultures....

www.usplastic.com

Huff747 · Aug 21, 2019

ca1ore said:
You can definitely replace just the tubing. I buy it in bulk and replace every 6 months. I've yet to replace the roller head after 18 months. Imagine you can probably get the tubing from places like BRS too.

1/8" ID x 1/4" OD x 1/16" Wall PharMed® Tubing | U.S. Plastic Corp.

Ideal for fermentation, synthesis, separation, purification, control systems, process monitoring, and protecting sensitive cell cultures....

www.usplastic.com

Couple more questions if you have a moment. I took a closer look at the tubing last night after work and looks like something I can do, did you use zip ties to hold the ends of the tubing on (looks like my DOS has them). And is that link the same place you ordered from? I'll probably order some, shipping is a bit annoying, but I didn't see an option at BRS.

ca1ore · Aug 21, 2019

It's a bit fiddly, but ultimately pretty simple. The tubing that I linked is the stuff I use (nominally 1/8" ID/1/4" OD). I just buy 10' at a time to help to mitigate the shipping cost (ends up around $5/foot with each foot being 3 replacements; so $1.75 versus $30 for a new head unit). You just pop the head off the pump, pry out the grey connectors (takes a bit of effort to work them out), snip off the old zipties, remove the old tubing, cut a new piece to length (use the old tube as a guide), press it back onto the barbs on the grey connector, replace with new zipties (the really small ones that you can get at HD), put a little o-ring lubricant onto the new hose and fit it back into the head unit. When replacing the head unit, make sure the + on the pump shaft aligns with the + on the roller assembly. You'll see what I mean when you take it off.

I imagine eventually a new roller assembly will be required, but even then it's not necessary to buy the full head unit as places like Avast sell the replacement roller for $9 - and it's better because it has four rather than two rollers.

Huff747 · Aug 21, 2019

Thanks again. I disassembled the head and pulled the tubing out to look for any holes and reassembled it last night (figured if I screwed it up I might have to buy a new head anyway) so all of that makes sense to me now. I'll probably order that same tubing you linked and replace it as I've been running it for a while.

Even last night after I reassembled everything I ran a calibration and it had to tweak it but when I ran the calibration again after the tweak it was on the money. Still figure it's wise to go ahead and replace the tubing. And thanks for the info on the o-ring lubricant. I wouldn't known to do that.