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Old 30-04-2016, 11:02   #31
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Re: How attach 1.5" waste hose to PVC tube?

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Originally Posted by ggray View Post
Hop, you are right, they don't make much sense, particularly the smaller sizes.

I understand that when the (nominal, remember) pipe sizes were established YEARS ago, someone over estimated the wall thickness needed for the smaller sizes, so when they realized that thinner would be sufficient, it resulted in a much larger ID than the nominal size.

But pipe sizes, though not close to exact, do refer to ID, not OD. Nevertheless, for a given pipe size regardless of schedule (as has been mentioned), all will all be the same.
Well sort of. Yes the sizes refer to the nominal ID of the pipe, until you reach 14 inch pipe, then it refers to the OD! Even though the nominal pipe size is mostly based on the ID, only the OD is consistent between schedules. It's just nuts.

Peggy those grey plastic hose barbs that are way too big are meant for use with that black semi rigid pipe they use for irrigation. That's a whole other ball of worms.

When buying pipe to hose fittings you should always take a sample of the hose or a caliper to measure with.

It looks like JR has found the solution for the OP's original question. I need to stock those in my store.
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Old 30-04-2016, 20:19   #32
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Re: How attach 1.5" waste hose to PVC tube?

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Peggie, I can't really follow your dimensions here...

I'll try to make them clearer: Fittings sizes should always be stated according to their OD... If they say it's 1.5 x 1.5, that SHOULD be the OD at both ends. Right?

So why is a nominal 1.5 x 1.5 thread-to barb (size clearly stamped into the fitting) actually 1.5" OD thread x 1.5" ID barb. That's only true of 1.5" gray sched 80 fittings, no other sizes or other materials. If you know why, you'll be first person I've found in 25 years who does.
No. Pipe size measurements are of the ID, although they are only approximate. Someone earlier had a link to actual pipe dimensions. The greatest variance is in the smaller sizes, IDs being much larger than pipe "size".

Where it can get confusing is that for a given pipe "size" if you need a different wall thickness (defined by Schedule 40 being standard I suppose, but also Sch. 20 thin wall, sch 80 heavy wall, and there is an extra heavy wall I think, maybe Sch 120??) the OD doesn't change because of the standard pipe thread and fittings, so the ID is varied.

1 1/2 inch NPT (National Pipe Thread) will have a much greater OD than 1 1/2 inch, because the ID is "about" 1 1/2 for sch 40. The 1 1/2 barb should be about 1 1/2 inch, not including barb, but probably a bit bigger.

Oh, the 1.5 X 1.5, I'm not sure where you are seeing that.
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Old 30-04-2016, 21:41   #33
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Re: How attach 1.5" waste hose to PVC tube?

Peggie, here is a link to a chart that shows the dimensions of the barb fittings you're talking about. You'll see that the barb that is marked 1-1/2" is actually about 1-5/8" OD.
That's why it's almost impossible to put a hose on those things.
http://63.156.201.113/INSTECH_INS-4_INSWD.pdf
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Old 01-05-2016, 05:04   #34
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Re: How attach 1.5" waste hose to PVC tube?

HopCar
Thanks, I'd never seen that before. And they are ASTM specs, so that means a lot.
Beside it are specs for polyethylene pipe, so it may be that the barb specs are for fittings specific to polyethylene pipe? I know I've seen "1/2 inch" barb fittings made of different materials, and the barbs were different, so perhaps there is an ASTM standard for barbs made for hoses, and even more than one standard.

Peggie, I rushed my last post. Clearly you were talking about 1.5 (NPT) X 1.5 (barb).
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Old 01-05-2016, 08:07   #35
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Re: How attach 1.5" waste hose to PVC tube?

Gray, yes those barb fittings are for use with that specific pipe. If you look at the chart you'll see that the 1-1/2 fittings are 1.66 OD and the pipe is 1.61 ID so it's a nice it.
So even though they are labeled 1-1/2 they are much closer to 1-5/8.

The only thing I've seen that pipe used for is cheap sprinkler systems and other irrigation projects. The pipe is semi flexible and very cheap.
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Old 02-05-2016, 11:29   #36
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Re: How attach 1.5" waste hose to PVC tube?

Not to beat a dead horse too much...


But I just opened the latest Practical Sailor to read that a barbed US standard fitting is not meant for sanitation hose. The proper one, as pictured, is smaller, and smooth.
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Old 02-05-2016, 13:24   #37
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Re: How attach 1.5" waste hose to PVC tube?

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All sanitation system hoses, and/or any hoses connecting to a below-waterline thru-hull should be DOUBLE clamped, with screws on opposite sides of the hose.
I didn't mean to suggest that they shouldn't be double clamped. I did use the plural "clamps".
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