Inline Filter: Glass-Filled Polypropylene vs bronze

Over the past couple of brewing session I have run into a problem during sparging, where some grain has made it down into my pump before the grain bed set, clogging the March pump and creating a general PITA.

I want to add an inline strainer to deal with this problem.

I have narrowed things down to two options:
1/ a bronze strainer such as this one: http://www.amazon.com/dp/B000LE7JUE/?tag=skimlinks_replacement-20
2/ a glass-filled polypropylene strainer such as one of the strainers here: http://vacmotion.com/In-Line Strainers.htm. I talked with tech support and these are made with food-grade plastic, even though the strainers are not FDA certified themselves.

I'm OK using either strainer during sparging, because the water temperature, about 170F, is reasonably within the temperature range of glass-filled polypropylene based on googling.

For simplicity's sake, the strainer will be mounted directly against the inlet port on my March pump. This means it will have near-boiling water running through it the last 15 minutes of the boil when I sterilize my counterpressure cooler.

This is where I start to worry about the glass-filled polypropylene leaching chemicals into the brew. I talked to the tech support guy at vacmotion and he said the temperature range provided in the specs had to do with strength under pressure and the plastic wouldn't leach. Since my filter is basically gravity-fed, I don't have have to worry about failure.

Regardless of what the tech support guy said, I'm still concerned about chemical leaching during the boil process. As an experiment I bought a small strainer for about $10 and boiled it for 20 minutes. There was no odor coming from the plastic or noticeable taste change in the water. So that at least is a positive.

My alternative is the bronze strainer. I'm not worried about leaching, but the tradeoff is a small strainer (I'm getting the 1" npt model), which may fill up with trub during the sterilization step.

I can always rig some bypass valves to avoid the strainer during sterilization of the CPC, but that adds some complexity that I'd prefer to avoid.

So I'm basically looking for someone with some expertise in plastics who can comment on the risk of chemical leaching from the polypropylene at high temperatures.

I'm guessing the screen in that fitting isn't even a square inch.

If so much grain is escaping your tun that it actually plugs up a beer pump (which are generally pretty tolerant of even whole grains randomly passing through) I would be surprised that fitting doesn't load up almost immediately, because a 20 mesh screen sure as heck isn't going to pass much of anything...

Cheers!

bump...anybody have more comments?

final bump...advice on the plastic component would be appreciated.

I am going to second what day_trippr said.
Sounds like you have a problem with the mash tun that still needs to be figured out.

Never good to place obstructions in the pump suction piping. I am with the rest of the crowd here in suggesting that the 20 mesh screen will also be WAY too small.

+1 to not putting a screen before the pump. I have yet to see a March pump get clogged with grain. Hate to say it, but I'd take a look at my false bottom or other processes that's letting that much grain through.

Adding my agreement here. I've never even heard of a march/chugger clogging with grain. You *do* have a false bottom or some sort of manifold/braid in your mash tun right?

Yup, fix it at the mash tun end. if it's getting to the pump, it'll clog either of the filters you've mentioned.

I did some more digging and it is probably a cavitation problem, not a blockage issue. I'll probably replace the pump with the newer ones with less cavitation issues (nice excuse for an upgrade), and remount the pump in a more optimal position.