PVC vs Brass ball valves

[seatotaler]

I'm in the process of introducing a fresh water engine flush tank system. So that the exhaust system won't have salt water in it when it's not in use. I'm “T” ing into the raw water line just before the water pump">raw water pump. My question is, which might stand up better to the salt water. A PVC ball valve or a Brass ball valve. I'm ruling out the bronze ball valve because of the cost and the application. There really isn't any significant pressure. The seacock is on the bottom of the hull, so about 3 feet below the water line. The ball valves will be about 6 inches below the water line in the engine room. 2 – 1 1/4” ball valves. One ball valve will open and close the salt water hose coming from the sea strainer, which leads to the seacock on the bottom of the hull. The other ball valve will open and close the hose from the gravity fed fresh water from the new tank, and vise versa. The ball valve coming from the fresh water tank will have salt water up against the one side of the ball when it's closed. The other ball valve will always have salt water on both sides. It will be a matter of just reversing the valves, so fresh water is circulated through the raw water side after each outing.
I don't see pressure being of any concern on either material. I'm more concerned about corrosion. The brass ball valve has a SS ball. I believe both ball valves use a teflon seal around the ball. My other concern, is the opinion of a surveyor, when that day comes.

[denverd0n]

Bronze would be best, but if you're ruling it out then PVC, absolutely. Brass should not be used in applications where it is exposed to sea water.

[SteveSails]

I wouldn't use brass or PVC for a valve below the water line, bite the bullet and get bronze. Don't know where in the world you are but if there is any danger of being in freezing weather PVC is not going to hold up.
OK, my opinion, your boat. If you insist on PVC look for the highest quality industrial valve you can find, not from the big box store. I'm sure there are other plastic valves stronger than PVC. Do some research.

[Hesti]

There are plastic valves which seem to be Bureau Veritas approved.


https://www.svb.de/de/trudesign-kugelhaehne.html


Mind you - I seem to remember darkly, that in the engine room, anything that can melt is not really welcome.

[seatotaler]

I'm in the pacific northwest so the likelihood of the raw water freezing and splitting the valve is unlikely. If it ever got anywhere near that temperature I would turn on the heat in the engine room.
The PVC valve is from the marine chandlery and their supplier is an industrial hose and fitting speciality manufacturer. The valve is rated at 150 psi.
The cost of the 4 valves required are $28 using PVC. $448 using bronze, including the bronze fittings on each end of the 4 valves.
I'm also leary of the life expectancy of a brass valve with salt water in it, so I think I've ruled that out.
The valves are about 16 inches away from the engines and if they got hot enough to melt, I'm thinking I might have a few bigger problems.

But as I mentioned I'm wondering what a surveyor might think.
Or perhaps an insurance adjuster might think if the boat should sink one day due to an unrelated reason.

[kas_1611]

When I swapped to Marelon, marine nylon, thru hulls a few years ago due to discovering the originals were standard domestic plumbing brass I upgraded the engine room valve to DZR or Corrosion Resistant Brass.

DZR isn't as resilient as true Bronze but it is marked with a big clear CR, has a green handle and will last far far longer than cheap brass (with the red handle). Anything in the engine room must be able to withstand the heat and nylon or PVC won't. Plus if PVC burns it gives off very toxic fumes that can kill in moments.

[Cheechako]

PVC becomes hard to turn. I have seen even schedule 80 fail several times in industrial applications too.
I would go with Bronze, but Brass wold likely be ok in that situation.

[sailorchic34]

Oh Oh, raising hand high, Pick me, Pick me.... I know this one.

Avoid Brass and PVC valves. Most brass ball valves has a chrome plated brass ball. It only looks like SS.. Not recommended on a boat or really anywhere in my book.

PVC will get brittle and the stem will fail at either the handle or ball. If you were to find a Polyethylene ball valve, that might work as well.

The weakness in any ball valve is where the stem connects to the ball.

What you want is a bronze ball valve with a Stainless steel Ball. Like this one: https://www.amazon.com/Apollo-70-140.../dp/B00634KZ8Y

Only $16.88 on amazon.

The SS is isolated from the bronze body by the teflon seals. No chrome to pit and it is far less prone to de-zincing. Strong, Fire resistant and +10 year lifespan. Probably less then 20 year life in salt water though. In all ball valves the stem is the weak link.

[ramblinrod]

+1 on sailor chics comments.

Below the (heeled) waterline, one should not have brass nor PVC.

Instead, use bronze (my preference) or Marlon (glass re-inforced Nylon).

I've replaced a lot of fairly young Marlon valves due to breakage.

Rarely replace bronze ball valves prematurely due to breakage other than from freezing due to improper winterizing.

Standard brass valves won't last in salt water and CR though better, won't last near as long as bronze.

When it comes to a potential failure most assuredly sinking the boat, SPEND THE MONEY to put in the correct product.

[SteveSails]

Do you need 1-1/4" valves on the FW side? For just a FW flush you don't need to run anywhere near full throttle so maybe 1" would be adequate. Prices of bronze valves and fittings drop dramatically from 1-1/4 to 1".

[Vortec]

Originally Posted by Hesti

There are plastic valves which seem to be Bureau Veritas approved.


https://www.svb.de/de/trudesign-kugelhaehne.html


Mind you - I seem to remember darkly, that in the engine room, anything that can melt is not really welcome.

Allmost everything can melt if the temperature is high enough...
😕⚓🏭

[ramblinrod]

One last note on this topic.

Any surveyor worth their salt would fault brass or PVC fittings below the waterline, and should flag it as requiring immediate repair before launching.

If one uses substandard materials and kills themselves due to an unnecessary failure, that is one thing, but if they kill their family or crew, that's another, and if they kill the unsuspecting subsequent buyer, that is yet another thing altogether.

If a family member of mine drowned, because a boat sank, because the owner (or previous owner) cheaped out on fittings below the waterline, they would have a lot of answering to do.

[Cheechako]

Originally Posted by sailorchic34

Oh Oh, raising hand high, Pick me, Pick me.... I know this one.

Avoid Brass and PVC valves. Most brass ball valves has a chrome plated brass ball. It only looks like SS.. Not recommended on a boat or really anywhere in my book.

PVC will get brittle and the stem will fail at either the handle or ball. If you were to find a Polyethylene ball valve, that might work as well.

The weakness in any ball valve is where the stem connects to the ball.

What you want is a bronze ball valve with a Stainless steel Ball. Like this one: https://www.amazon.com/Apollo-70-140.../dp/B00634KZ8Y

Only $16.88 on amazon.

The SS is isolated from the bronze body by the teflon seals. No chrome to pit and it is far less prone to de-zincing. Strong, Fire resistant and +10 year lifespan. Probably less then 20 year life in salt water though. In all ball valves the stem is the weak link.

Good comments. One thing though, I've often wondered if a Chrome ball is actually better. What is in SS that makes it good? A small bit of Chromium. How does SS react in a closed oxygen depleted environment (like while sitting closed/unused)? It pits and corrodes.
OK, carry on.

[seatotaler]

Thanks sailorchic, you made some valid points. However the price you mentioned for the amazon valve was for the smallest size.
When you mentioned that PVC valves get brittle, what time frame are you talking about?

I mean I'm going to be inspecting my raw water side of my exhaust every 4 years now. It would take less than an hour to replace all 4 valves at a cost of about $28.00 Canadian. I'm not trying to penny pinch but I don't like spending money where it's not needed.
Thanks for everybody else's input too.

[Cheechako]

Originally Posted by seatotaler

Thanks sailorchic, you made some valid points. However the price you mentioned for the amazon valve was for the smallest size.
When you mentioned that PVC valves get brittle, what time frame are you talking about?

I mean I'm going to be inspecting my raw water side of my exhaust every 4 years now. It would take less than an hour to replace all 4 valves at a cost of about $28.00 Canadian. I'm not trying to penny pinch but I don't like spending money where it's not needed.
Thanks for everybody else's input too.

Another option for what you are doing; I think you said these are well above the waterline, why not a good bronze gate valve? I know people dont like them in boats but there are many out there, even below the waterline, that last 20 years. Just thought for the $ conscious. But above the waterline, heck any old ball valve.