effects of main line capacity using stainless mainline fittings vs. plastic fittings

Does any one have any real world experience on the effects of main line capacity using stainless steel couplings vs plastic couplings. A one inch mainline stainless coupling is a full 1 inch inside diameter where a 1 inch plastic coupling is 3/4 inch inside diameter. The difference does not sound like a lot but it figures out that the 1 inch stainless steel coupling has about 1.75 times the area of the plastic one. Would this mean that a 3/4 inch pipe using stainless steel couplings would have the same carrying capacity of a 1 inch pipe using plastic couplings.
I am trying to find out as I have a 2500 foot mainline to install this spring just to get to the sugar bush. A 3/4 inch line is way easier to carry. The system will be on 3/16 with no vacuum pump.

Thanks luke

We use stainless couplings. But i wouldn't downsize your mainline just because of the stainless couplings.

My real world experience is in the fire service with smaller couplings on larger hose. It doesn't change the capacity to any degree. The only time it makes a difference with maple tubing is if you have vacuum. The stainless fittings can transfer vacuum better when you are approaching maximum rated capacity of the tubing. If the plastic fittings are restricting flow your tubing is probably undersized to begin with.

Slush and ice chunks pass through stainless fittings, plastic seems to catch them.

For sapline, you should upsize the pipeline if: gradient is only slight, you have many fittings, greater number of laterals, and longer distances. But I would say that sags in your line are the absolute most critical problem which will be severely aggravated by any flow restrictions caused by narrow couplings. These sags will always freeze hard with partial or full sap and be the last thing to thaw (or as we say in Vermont - unthaw).

For several years we used 1/2" and 3/4" poly mainline and used plastic fitting. Then we upgraded to 3/4" and 1" lines. Then we started looking into stainless fittings. There are two choices....plumbing and maple. The plumbing are thinner than the plastic and have a little better barb for more grip. The maple are much thinner and the barbs are much sharper. You can see the images I posted below are of a section of mainline I cut out. We have upgraded our mainlines to 1" and use all stainless fittings. They do not cost a whole lot more thank the plastic, hold better, creat less turbulence, and give less area for bacteria to grow.

There is not much relevance to pressured lines because the sap is moving downhill by gravity. Often times our mainlines are not full. They trickle down and any ledge in the line can upset the flow. If the pipe is near full and you do not have a dry line the transfer of vacuum could be interrupted or the flow of sap could have turbulence.

Mike



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