The cult of the Proper Flanged Thru-hull

[Simi 60]

Originally Posted by rslifkin

Depends on the boat too. On many powerboats the sinks are high enough to gravity drain above the waterline, for example. I'd bet that's the case on Simi's boat.

Correct
But even on previous sailing cats I had, sinks in hulls were well above waterline and shower sumps pumped out above waterline.

[Q Xopa]

Originally Posted by goboatingnow

CW602N brass from good quality manufacturers is entirely suitable for seawater and will remain suitable for decades . This is behind the DNZ marking ( CR)

There’s no field evidence that flanges are needed

I think there is evidence of a number of non seawater suitable brass thru hulls being snuck into boats.

I'm pretty sure there is no evidence that flanged Seacocks are unnecessary.

There are no Brass Flanged Thru hulls. They are all marine bronze.

If you are trying to evaluate if flanged or non flanged is better it's pretty obvious by simply looking at them.

I guess some people are happy to save some money.

We pays our money, we takes our chances.

[skipgundlach]

Originally Posted by teneicm

Holy smokes, you ARE a full-fledged cult member! You went to all that trouble for an above-waterline thru-hull? I mean, it's great, but a lot of work for something not nearly as critical as other thru-hulls.

Bennie puts their sink drains above the waterline???

YUUCK.

They wouldn't do well with the keel-cooler type of insert for galley sink drains like Isotherm and others use, then, would they?

https://www.suremarineservice.com/Ga...ter-Cooled-SP/

More on Drain coolers, and through-hulls in general:

https://www.sailcloudybay.com/more-thru-hull-work/

[poiu]

Originally Posted by Jetx

Our boat had DZR brass thru-hull fittings and ball valves from the factory. I didn’t trust them and decided to replace them wholesale when we bought the boat (15 years old at the time).

TWO of the thru-hulls snapped off completely as I was trying to coax the hose off of the attached barbed fittings. Very scary.

DZR isn’t meant to do this. Brass is. Are you sure they were DZR? Do you have pictures?

[goboatingnow]

How do you know they were DNZ. they would normally be marked “ CR”

[goboatingnow]

Originally Posted by Q Xopa

I think there is evidence of a number of non seawater suitable brass thru hulls being snuck into boats.

I'm pretty sure there is no evidence that flanged Seacocks are unnecessary.

There are no Brass Flanged Thru hulls. They are all marine bronze.

If you are trying to evaluate if flanged or non flanged is better it's pretty obvious by simply looking at them.

I guess some people are happy to save some money.

We pays our money, we takes our chances.

Yes there is certainly evidence of poor quality in the after market segment.

No one suggested that flanged fittings are unnecessary. They and I have put forward that good quality mushroom BSP fittings are adaquate and will pass ISO strength checks once properly fitted

[rslifkin]

Originally Posted by goboatingnow

Yes there is certainly evidence of poor quality in the after market segment.

No one suggested that flanged fittings are unnecessary. They and I have put forward that good quality mushroom BSP fittings are adaquate and will pass ISO strength checks once properly fitted

What does the ISO strength test consist of? Just because it's a standard doesn't mean it's adequate to cover the worst case of a person falling against it while working on it or similar. The ABYC standard is intended to cover that scenario.

Personally, I'd rather go for the better fittings and proper flanges. It doesn't cost that much more to do it right (especially if you use the flanged adapters so the valves become easily and cheaply replaceable ball valves instead of expensive seacocks).

If done right and with good parts, then in most cases the install will last a very, very long time. I still have a few 36 year old flanged bronze seacocks on my boat that are intact, show no signs of dezincification, and as far as I can determine are perfectly fine for continued service.

[Bill Seal]

Why not just make the thru hull stem and flanged nut over-kill thick, like 1/4" wall thickness, the metal isn't that expensive.

[s/v Jedi]

Originally Posted by Simi 60

Nope, had them come out of the hull no further than a skin fitting tail, threaded fiberglass tube, ball valve onto that.

I have seen that for intakes on metal boats, which is great, but not in fiberglass… I think it’ll be okay but I’m not sure it will pass any ISO/ABYC tests…

[teneicm]

Originally Posted by skipgundlach

Bennie puts their sink drains above the waterline???

YUUCK.

Why would you put another potential failure point/ hole in your boat if you didn't have to? Most boats I've seen put sink discharges, AC discharges, bilge pump discharges, etc above the water line if possible.

[goboatingnow]

Originally Posted by rslifkin

What does the ISO strength test consist of? Just because it's a standard doesn't mean it's adequate to cover the worst case of a person falling against it while working on it or similar. The ABYC standard is intended to cover that scenario.



Personally, I'd rather go for the better fittings and proper flanges. It doesn't cost that much more to do it right (especially if you use the flanged adapters so the valves become easily and cheaply replaceable ball valves instead of expensive seacocks).



If done right and with good parts, then in most cases the install will last a very, very long time. I still have a few 36 year old flanged bronze seacocks on my boat that are intact, show no signs of dezincification, and as far as I can determine are perfectly fine for continued service.

The iso 9093:2021 strength standard is considerably more comprehensive then ABYC and has several tests on both the fitting and assembly

[goboatingnow]

Originally Posted by skipgundlach

Bennie puts their sink drains above the waterline???



YUUCK.



They wouldn't do well with the keel-cooler type of insert for galley sink drains like Isotherm and others use, then, would they?



https://www.suremarineservice.com/Ga...ter-Cooled-SP/



More on Drain coolers, and through-hulls in general:



https://www.sailcloudybay.com/more-thru-hull-work/

My Bavaria has just two fittings underwater. The test including all sinks are above the static water line. To me that’s good practice

[skipgundlach]

Originally Posted by teneicm

Why would you put another potential failure point/ hole in your boat if you didn't have to? Most boats I've seen put sink discharges, AC discharges, bilge pump discharges, etc above the water line if possible.

Heh.

I don't know Bennies.

But in my and most boats I've been aboard, the sink isn't far above (maybe a foot) the water line, and unless it were rather more outboard, running a line to exit over the water might be interesting...

But, given the likelihood of food products being part of that discharge, putting it under the boat also (to me) is more appealing.

That said, while I took them out, indeed our boat's refrigeration, and AC, both exited above the water line.

Our bilges, to provide a secure vented loop, were teed into our cockpit scupper drain lines...

[noelex 77]

Originally Posted by s/v Jedi

Those are called “standpipes” and should raise up to above waterline. They don’t require valves.

We also have standpipes on all inlets and outlets.

I still think seacocks on top of the standpipe are sensible. Belt and Braces.

The standpipe is well above the waterline so a break or leak in the attachment between the standpipe and the hose will not let water into the boat unlike a normal through hull, but it can still set up a syphon in some (admittedly unusual) circumstances. An ability to turn off the water supply, especially when leaving the boat is helpful.

An advantage of standpipes is the seacock can be removed and serviced or replaced in the water without any risk of flooding the boat. Likewise the seacock can be damaged, leaking or defective without risk, but this does not mean that seacock serves no purpose.

[pcmm]

Originally Posted by goboatingnow

The iso 9093:2021 strength standard is considerably more comprehensive then ABYC and has several tests on both the fitting and assembly

I'm not sure I would beleive that. Rob Collins has done tests of the thrull/ballvalve assembly and the results are a bit worrying. A properly installed flanged seacock and the flanged seacock assembly wins hands down. If I had access to the content of "iso 9093:2021" I'd like to see what "Strength" it specificies as ABYC specifies 500lbs on the inboard most end of the seacock assembly

Have a look. I wouldn't want my seacock assembly flexing like this!

https://www.youtube.com/watch?v=YzKb...mpassMarineInc

.

compared to:

https://www.youtube.com/watch?v=KKTK...mpassMarineInc

.