Polypropylene couplings

My system is all stainless with the exception of the March Pump (when I hit the lottery, I'll get the stainless pump head). The pump supplier says, just like AHS, not to connect the pump head directly to the metal piping. AHS only sells the 1/2" couplings. I need (1) 1/2" and (1) 3/4". All of the other couplings I see locally (WW Grainger and a Mom & Pop supply house) are rated at 150F max temp. Sooo, my question is any ideas on a substitute? Maybe cpvc? I need something that will take CIP, Oxyclean or PBW. Suggestions, comments? Thanks - Dwain

All the photo's I have seen show people using metal couplings with the March pump, at least that's what it looks like. Some teflon tape and carefully screwing it on should do the trick. High temp plastic couplings are not so easy to find. Here is a chart of info on various plastics Comparison Table for Plastics.

CPVC is not rated to boiling temps.

Dwain said:

My system is all stainless with the exception of the March Pump (when I hit the lottery, I'll get the stainless pump head). The pump supplier says, just like AHS, not to connect the pump head directly to the metal piping. AHS only sells the 1/2" couplings. I need (1) 1/2" and (1) 3/4". All of the other couplings I see locally (WW Grainger and a Mom & Pop supply house) are rated at 150F max temp. Sooo, my question is any ideas on a substitute? Maybe cpvc? I need something that will take CIP, Oxyclean or PBW. Suggestions, comments? Thanks - Dwain

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I think you may be misinterpreting what is meant when they say not to connect the pump head directly to the metal piping. I would request some clarification on that from the mfg. or AHS. I would ask why not?

I think what they are getting at is they don't want the pump/motor hanging from the pipe only with no other support. I think that's what they should have told you instead. Metal fittings are not the issue. IMO, the solution is to mount the pump with an appropriate bracket then hook up whatever pipe/hose you want to, metal or otherwise. I would plumb it inline using pipe unions so it could be removed easily for occasional maintenance. I could be wrong on this, but I don't think so this time.

In-line with cat22 I think the intent behind the warning is to keep the pump from being directly coupled to a system that could potentially vibrate the holy crap out of a plastic head thus causing an unexpected failure.

Given the head is plastic (Ryton, IIRC) there is no galvanic corrosion potential so it all comes down to shear and the pump head will lose.

I don't think he is misinterpreting what AHS said as this is on the website:

The March Pump also requires two 1/2" NPT couplings. One is for the "in" connection, and one is for the "out" connection. To avoid damaging the pump head, the use of polypropylene couplings is recommended because threading metal fittings onto the pump head can damage the pump's threads. See the option below to add a pair of couplings.

What they fail to take into account is the working temperature range of polypropylene. Also it has been my experience that mating plastic threaded pieces, especially different kinds and manufacturers proves to be a challenge. Throw in high heat expansion/contraction and it gets harder to accomplish.

You may be correct, but it seems to me that what they are worried about is the possibility of you over tightening the fittings and damaging the threads. Properly threading metal fittings onto the pump head should not cause any damage at all, the key word being, "properly". I've been doing it for years without problems.

GilaMinumBeer has a good point about vibration potentially causing problems. I suppose expansion of the metal pipe should also be considered. That all depends on the system configuration. In any case, I would not hang the pump from the piping.

I would try to find some nylon pipe fittings. I'm using some from McMaster-Carr which are Garden Hose x 5/8" barb on all my hoses with no problems whatsoever. They are cheap too!

Those threads ARE really soft. I know at least one person who accidentally (and easily) cross-threaded a brass fitting onto the pump head. It took a little filing on the threads to get things working right again. If you use brass/SS directly, just be really careful as you thread things together, and don't over-tighten the fitting.

O.K.,
I've been researching this. I called March Pump. The March Pump Tech. said that he could not recommend a suitable material to use as a transition between the polysulphone (polysulphide) pump head and the stainless piping. He did say that the Guy that would know, wasn't in and asked that I call back later.
I worked in the chemical industry for many years. We routinely connected dissimilar materials. Even stainless and carbon steel to various plastics. We rarely needed anything to be food grade, so it normally wasn't an issue.
As most of us are aware, when dealing with high temperature, there is less danger of a "plastic" coupling failing than the chemical properties becoming unstable and "off gassing" into the product.
I spent quite abit of time with a Mcmaster-Carr Technical Rep. (Dave) trying to find a material that would handle 212F and still maintain its FDA rating. We looked at Polypropylene, Polyethylene, HDPE, LDPE, PTFE, Kinar, Nylon and sevaral others "blends" of Fluoroplastic fittings. The only thing that was close was schedule 80 CPVC. It is only good to 200F. The rest of the materials that started out FDA approved to begin with were only rated at 180F max. Kudos to Mcmaster-Carr's Tech. help section for all of their effort.
Then, I called March Pump back. I talked with Hans (apparently the Guy that knows), and he said that there was no problem hooking the pump directly up to the stainless piping. Just be sure that I didn't cross-thread, over tighten etc.. He said it would not void the warranty or otherwise violate the rules of international trade.
Sooo, I'm off to the shop to hook up my pump! Sorry for the long post, but I felt this was a very important piece of our hobby and wanted to get the straight info.
Now you know, and knowing is half the battle - G.I. Joe
Luck - Dwain

Yes, that's exactly why---I had the same question when I bought mine---and it's just because too many people have ruined their head by cross-threading. Just be careful!

I felt the same... I purchased the MP from Austin HB and opted for their plastic fittings as well... just in case you know... But i believe I will be going with my metal fittings as I have already plumbed everything in Copper... We will find out today I guess

Cancel this post.

According to March pumps and others, 3-4 wraps of Teflon tape should be used on the pump threads and then you can use metal or plastic fittings, hand tight and then wrench it 3/4- 1 turn beyond. Of course I never could understand how they can measure hand tight as some people can really crank it much tighter than others with the hands.

I considered the warning myself, but just opted to make sure that the coupling's threads were such that I wouldn't have assembly or dis-assembly issues. Ever notice that hand threading some pieces together, that they do not like to engage that well, without wrench force? This is the situation I am warning of, because the imperfections in the stainless coupling are in a very strong material, and it won't be the stainless threads that 'adjust' when screwed together with plastic threads. If couplings are not cleaned up by tap or previous metal to metal connection, the threads could rip the plastic on the way in, or alternately on the way out, as it is disassembled.


The threads that are put in are called Nation Pipe Threads, they are tapered, and put in by machines that run thousands and thousands of pieces. The threads could be rough, torn, poorly cut, or dinged from contact with other things.

I first chased the threads with a pipe tap, which is tapered and has the same thread pitch as the coupling. This insures that the threads are true and won't catch or tear the plastic. For those that do not have access to a pipe tap, or can't swing the cash (they're not cheap) I suggest at least pre-fitting the couplings to another metal part to smooth them a bit, before assembling to plastic.

Its funny last night I had a "Nightmare" as you might call it about stripping the threads on my new march pump that I got... And then I rememerbed when I woke up that I have the polypro Couplers... I am jointing mine together with Copperand am going to use my pipe tap first to make sure everything threads together just right... No sense in hurrying on something so expensive to replace...

I use poly disconnects on my system, but I use a SS Ball Value connected to the outlet to adjust the outflow of the pump. I have not had any problems, but I think the theme is to make sure you use a healthy dose of Teflon tape, and use caution when screwing in metal to the plastic, and do not force it on.

Maybe a little off topic but does anyone use bronze head pumps?
http://www.homebrewing.org/March-Pump-125_p_1015.html

That's what I have and I don't think its much more expensive.

I don't see much of an advantage for the bronze head... I'd rather hold out for the SS one...

Think of it from the retailer's perspective. You just sold someone a new pump. They get it home and cross thread the hell out it in some drunken stupor. Do you play hardball and blame user error or eat it and send a new pump head out? Frankly, if it were me, I'd send all march pumps out with 1/2" stainless couplings already threaded onto the head. Remove and replace at your own risk.

A march pump is on my list of additions. I have no interest in QD's and just want a simple 1/2" barb for my silicone hoses. I looked at bargainfittings.net and mcmaster and did not see a female 1/2" NPT to 1/2" barb outside of this for $16.50 McMaster-Carr which seems overkill.
I suppose I could use threaded couplings and male adaptors but that seems needless.
ideas or suggestions?

Here ya go:

Plastic Tanks, Plastic Buckets, Plastic Bottles, Labware, Plastic Tubing, PVC Pipe, Plastic Sheet - United States Plastic Corporation ®

I use the Barb x Garden Hose Thread type, but you can also get them in the NPT thread. They are dirt cheap and I've been using them on my RIMS for a long time without any problems whatsoever. They also don't get too hot to handle like SS or brass fittings often do. QD's don't interest me either. I don't have to switch hoses but a few times during a session, so it's not of major importance in my case.

Catt22
Thanks for the link, which ones do you use specifically? The march pump from AHS has 1/2" NPT in and out, I know some of the pumps are 3/4"

The pump I have is a Little Giant, but it's basically the same as a March and it has 1/2" NPT threads on the input/output ports. I used brass adapters to transition from the 1/2" NPT to male garden hose thread. The hoses are 5/8" ID and this is the barb x 3/4" GHT I use on both ends of all hoses. I like to use female couplings on all hoses and males on all the equipment. The reasoning is that it doesn't matter which end of the hose you use as it will always be a female and connect to any of the equipment:

Nylon Swivel Female Insert x 3/4" GHT - US Plastic Corporation

No need to worry about using brass or SS fittings directly on the pump. Just avoid overtightening them and be careful not to cross thread. They seal very well just snugged up with some teflon tape on the threads. You can get the brass NPT x hose thread adapters at Home Depot. You might need another reducer or adapter to get from 3/4" NPT to 1/2" NPT on the pump. I think you can get these in nylon as well. The U.S. Plastics web site can be challenging to navigate at times, but their selection is great. They also have good prices on PVC braid reinforced tubing which is what I've been using. There's a choice of wall thicknesses for the tubing. I bought the thicker version as it resists kinking and collapsing much better than the thinner walled stuff.

I found a direct female to barb in 1/2" too bad they're not stainless, or even hi temp plastic like polysulfone
http://www.brewmasterswarehouse.com/products/Brass-Hose-Barbs-FPT-12-FPT-x-12-Barb-0101743
update: I found in stainless what I was looking for at a reasonable price:
http://morebeer.com/view_product/17422/102353/Stainless-_1_2"_FPT_x_1_2"_Barb

bdavanza said:

I found a direct female to barb in 1/2" too bad they're not stainless, or even hi temp plastic like polysulfone
http://www.brewmasterswarehouse.com/products/Brass-Hose-Barbs-FPT-12-FPT-x-12-Barb-0101743
update: I found in stainless what I was looking for at a reasonable price:
Stainless- 1/2" FPT x 1/2" Barb | MoreBeer

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FWIW I foresee a couple of potential problems using those pipe thread x barb fittings on your pump. Pipe thread fittings are not intended to be installed and removed repeatedly and this is especially important when using them on the plastic pump head threads. Garden hose thread is preferable for this type of application. The threads are much coarser which makes them more durable, faster to connect and less prone to cross threading. Pipe threads are relatively fine and provide none of those advantages. The other issue with metal fittings is that they are very hot to the touch so you often need to use gloves. It's not that they are hotter than the plastic, but they retain more heat and conduct it much better. It's a very significant difference. Try removing a hot metal fitting with your bare hands and you will see what I mean. So, I would suggest using adapters on the pump threads to get from pipe thread to hose thread and those can be metal as you will not be touching them directly under normal usage. Then use the nylon fittings on the hoses to mate with the adapters. The nylon fittings can handle the hot wort without problems. They are dramatically less expensive too. That's kind of nice.

The intent is to save wear and tear on the pump head threads by using the adapter to hose threads. The pump heads are expensive to replace if you damage it by cross threading or otherwise ruin the threads. Hose threaded fittings also use a gasket to make the seal. Pipe threads require teflon tape or other type of thread seal. You don't want to re-apply the tape or seal each time you remove or attach a hose to the pump or anything else.

The other issue with the 1/2" barb fittings is the small inside diameter. The barb fits inside a 1/2" ID hose, but the ID of the barb piece itself is much smaller at approx 3/8" ID. This is a considerable restriction and will reduce pump performance. This is most important on the suction side of the pump.

Most of the issues people have with these mag drive pumps could be eliminated by using larger diameter hoses and fittings. Using shorter hoses is also advantageous.

+1 on not repeatedly disconnecting/connecting the couplings on the pump. As the pump head/threads on both the pump and coupling get hot, they will become increasingly easier to cross thread. Mine had a little imperfection on the pump threads and I had to straighten it out with a file because it didn't want to thread straight. Luck - Dwain

I would have no intention of removing the barb once placed correctly, unless I was going to repurpose the pump. I use silicone hoses and plastic quick clamps, which work great and I've never had one pop off. I just want barbed ends on a pump. I realize I've kind of stolen this thread, my apologies, link to quick clamps:

Austin Homebrew Supply

What do you know, I get a march pump for xmas and now the female fittings are on backorder.