Nylon vs PVC fittings? Which is best?

[Bigjim]

I'm reworking several systems on my boat and noticed that most hose fittings come in both nylon and PVC versions. Both offer MIB and hose barb connectors and adapters.

I have the potable water system, the engine intake and the waste water system in need of replacement or redesign.

So, the obvious question is: Which one should I pick for these replacements?

What are the advantages and disadvantages of each?

[peghall]

I'll let others advise you on what to use in the engine intake. When it comes to the sanitation ("waste water") system..If it connects to a below waterline thru-hull use PVC or Marelon. If it's on the outside of the hull (thru-hull), use anything BUT nylon (it has -0- UV resistance). ALWAYS double clamp all hose connections, with screws 180 degrees apart (at least 90 degrees if access or location makes 180 impossible). It's NOT necessary for thread-barb hose connectors to have actual barbs...the barbs can be smooth. Be careful not to OVER-tighten threaded tank fittings. They're NPT standard, which is slightly tapered--TOO slightly to see with the naked eye when looking at a female fitting that's only an inch long. But it's enough that tightening the male thread-barb fitting more than a full turn past hand tight will crack it...it not immediately, soon.

Replace your holding tank "vent" thru-hull with an open bulkhead (aks "mushroom" thru-hull. You'll find the reason for that in my book (see link in my signature below) or in any of my zillions of posts to this site, where you'll also find my sanitation hose recommendations.

Fresh water system: it depends on the type of plumbing (PEX, for instance). And I'll let others advise you about that too.


--Peggie

[Bigjim]

Originally Posted by peghall

Replace your holding tank "vent" thru-hull with an open bulkhead (aks "mushroom" thru-hull. You'll find the reason for that in my book (see link in my signature below) or in any of my zillions of posts to this site, where you'll also find my sanitation hose recommendations.

--Peggie

I bought your book a long time ago. What page is the mushroom vent on?

[peghall]

Whether it's in the copy of my book you have depends on whether you have the very outdated 2003 1st edition, or the 2016 "NEW Updated, Revised and Expanded" 2016 2nd edition. If so, you'll find a photo of one on page 41. They're available in marelon, nylon (NOT recommended!), PVC, stainless or bronze.


--Peggie

[chasmains]

Please post your link, Peggie. I couldn’t activate. Thanks, C

[Scubaseas]

Hey Peggie,

Have bought both editions of your book. Brilliant book and excellent resource for any boater or RV owner. Just wanted to say thank you for all the support you offer on this forum. Kudos to you for all the time you selflessly take out of your life to help other people.

[Cheechako]

I would not use either below the water line. Also, nylon will turn to dust in the sun. Tried to get a hose off one once in the hull side and it simply snapped off the mushroom which was degraded by UV and"dusty" looking.. Pretty sure it was nylon, felt like it, was semi transparent white ish. Not ABS/PVC style bright white.
Nothing but metal or Marelon below the water or where it may cause flooding for me. I have used hardware store brass/bronze many times without issues in water systems etc. (not attached to a seacock or bronze valve!)
I have seen large diameter grey PVC in schedule 80 break readily in industrial water use.

[NorthCoastJoe]

I would go with 1/2" PEX for the potable water. If you don't have a crimper Shark Bite fittings will work just cost more. Include an accumulator in the system to take out the water pump pulses.

[peghall]

Originally Posted by chasmains

Please post your link, Peggie. I couldn’t activate. Thanks, C

If you're referring to the link to my book listing on Amazon, just clicking on the title in my signatureat the bottom of all my posts should bring it up. But just in case...


http://www.amazon.com/New-Get-Rid-Bo...dp/1892399784/


And I thank you for your interest in it!


--Peggie

[peghall]

Thank you for the kind words! I enjoy helping people solve problems--better yet, prevent them! It also forces me to use my brain, which may keep it functioning longer...at least I hope so!



--Peggie

[Bigjim]

Originally Posted by Cheechako

I would not use either below the water line. Also, nylon will turn to dust in the sun. Tried to get a hose off one once in the hull side and it simply snapped off the mushroom which was degraded by UV and"dusty" looking.. Pretty sure it was nylon, felt like it, was semi transparent white ish. Not ABS/PVC style bright white.
Nothing but metal or Marelon below the water or where it may cause flooding for me. I have used hardware store brass/bronze many times without issues in water systems etc. (not attached to a seacock or bronze valve!)
I have seen large diameter grey PVC in schedule 80 break readily in industrial water use.

That helps a bunch. But I'm looking at what the difference is between nylon and PVC INSIDE the boat and NOT outside or below the waterline. Nylon is softer, more flexible and may resist bending more than PVC which is harder and less flexible.

I see that PEX is often paired with hard PVC. I do have a crimper for PEX fittings and will be redoing my entire potable water system next year.

I like using metal whenever possible, but nylon and PVC are available easily from most box stores. Most water systems don't put a lot of stress on these fitting. We're talking low pressure water and such. But, I'd like to set up this system once and not have to replace items 5 years down the line.

So, is there any qualitative difference between identical nylon and PVC connectors?

1. Salt/fresh water wash down?
2. Fresh water plumbing/supply?
3. Waste hoses and holding tanks?

Bronze and brass are not as readily available. I've had to order items from multiple sources to fit my system design.

[mitiempo]

Originally Posted by peghall

......If it connects to a below waterline thru-hull use PVC or Marelon.
--Peggie

PVC below the waterline attached to a thru-hull will not pass a survey.

Use Marelon (Forespar or TruDesign) or bronze.

[finefurn]

Originally Posted by NorthCoastJoe

I would go with 1/2" PEX for the potable water. If you don't have a crimper Shark Bite fittings will work just cost more. Include an accumulator in the system to take out the water pump pulses.

May be a dumb Newbe question but, What is an Accumulator ?

[peghall]

TY for the correction!


--Peggie

[mitiempo]

Originally Posted by finefurn

May be a dumb Newbe question but, What is an Accumulator ?

An accumulator is a tank T'ed in line after the pump. It has a diaphram in it with air pressure on the top end and the water enters the bottom. It smooths out the pump's effects when it shuts off. If large enough someone can get up for a drink of water in the night and the pump will not run.

https://www.amazon.ca/Jabsco-1881000...95336707&psc=1