APEX DOS loses prime

[dwfain]

Anyone else have the APEX DOS lose prime? I am dosing RedSea ALK and CA and both lose the prime on all three of my systems. I drilled a small hole in each cap to keep the bottle from collapsing, could that be the reason.

 

[SuncrestReef]

This is usually caused by a bad connection where the tubing meets the DOS. I always heat the tubing in a cup of near-boiling water to soften it before connecting to the compression fitting for an air-tight seal. Works great for me.

 

[Hairyteeth]

Same as above loose fitting on the dos between connection of hose and heads

 

[TexanCanuck]

The DOS pumps are peristaltic pumps and do not require priming ... as long as they have air-tight connections between the suction side of the pump and the fluid you are pumping they will draw fluid!

Like the previous posters, I strongly suspect the issue is in your tubing connections ... either where it connects to the suction side of the pump, or where it connects to your reservoir.

Personally, I find the tubing that comes with the DOS unit to be highly prone to this problem. Instead, I recommend using a silicon-based tubing of the same dimensions ... solves the problem every time!

Here's what I use:

 

[dwfain]

Thanks, order some new tubing. Anyone seen or had experience with the adapter that converts these fittings to the push to connect fittings for more rigid hoses? I've seen them somewhere on R2R but cannot find them now.

 

[Hairyteeth]

… no but I saw this thread back up and had a second add on thought, I would keep an extra dos head on stock, I had a leaky one that I over tightened trying to fix, and ruined, ultimately replacing the head/ connections was what fixed it. In This case it was me human error but was nice I had an extra!

 

[homer1475]

Never went the push fit fitting route.

I just heated up the end of the RO/DI line, pushed onto the stock connector, cinched up the nut. been working that way for the last 3 years. I never loose prime.

 

[TexanCanuck]

I've seen a few photos here on R2R showing push-to-connect fittings on the DOS ... but I'm not sure it's worth the effort.

Here's my thinking:
1) once you install the tubing, you are likely to leave it in place for a long period of time. In three years I've never had to remove my tubing ... so I don't see the benefit of the push-to-connect fittings
2) these fittings will add a second leak path for air ... using the provided fittings there is only 1 place for air to get in ... once you add the push-to-connect fittings there are now two (between the pump head and the fitting, and then between the fitting and the tubing)

Bottom line ... it's neat to look at but not sure there is a functional reason for using push-to-connect fittings on the DOS

 

[biecacka]

So I have a DOS that loses prime as well. I have push-to-connect fittings. I bought it used and it came that way, I’ve used it as such for years, but a few weeks ago it started acting up and now it doesn’t move any water. Any ideas??

corey