Through Hull Advice Needed

[Frayed Knot]

I’m steadily replacing my 40+ year old through hulls with Tru Design. Four so far without difficulty but two of the next four have me stumped. They each serve twin deck drains each side of the cockpit.
Although there doesn’t appear to be any electrolytic degradation they are old & worn (like their owner) & similarly tend to seize up on a regular basis.
Naturally the hoses run downwards, close to the hull & so the valve needs to be parallel to the hull (as shown in the photo) but I cannot find anything in a similar material to form a 90deg bend from the skin fitting.
The existing skin fitting is approximately 45mm diameter & the twin hoses are 32mm I/D.
I could, of course, use a metal elbow between the Tru Design through hull & valve but that rather goes against the grain (and is advised against on the Tru Design website) & would be difficult to effectively bond to the anode system.
Any advice (on the seacock issue) would be gratefully received.
And yes, I know the hoses should be double clamped - the new ones will be

 

[Tranona]

Just replace with a DZR ball valve (not a gate valve), through hull and elbow. Will last just as long as a Tru Design (ie virtually forever) and be cheaper. No basic objection to fitting composite through hulls but DZR is just as good, more choice of fittings and usually cheaper.

In fact that elbow looks fine and I would just replace that gate valve with a DZR ball valve. The failure points on through hulls are dezincification of brass fittings and spindles of valves, particularly gate valves. Your elbow looks like bronze and will last forever, and the tail and Y piece looks OK, so the only weak point is the gate valve which is the worst for spindle failure.

 

[Frayed Knot]

Just replace with a DZR ball valve (not a gate valve), through hull and elbow. Will last just as long as a Tru Design (ie virtually forever) and be cheaper. No basic objection to fitting composite through hulls but DZR is just as good, more choice of fittings and usually cheaper.

In fact that elbow looks fine and I would just replace that gate valve with a DZR ball valve. The failure points on through hulls are dezincification of brass fittings and spindles of valves, particularly gate valves. Your elbow looks like bronze and will last forever, and the tail and Y piece looks OK, so the only weak point is the gate valve which is the worst for spindle failure.

Thanks. Yes, that’s certainly an option & makes sense.

 

[john_morris_uk]

And you REALLY don’t need to connect metal through hulls etc to your cathodic protection.

 

[Tranona]

And you REALLY don’t need to connect metal through hulls etc to your cathodic protection.

+1

 

[Frayed Knot]

And you REALLY don’t need to connect metal through hulls etc to your cathodic protection.

That surprises me.

 

[Tranona]

That surprises me.

Should not be a surprise if you understand the process of galvanic action in seawater. The key thing is that seacock are not connected to any other dissimilar metal, unlike, say a stainless propshaft and a yellow metal propeller, or an aluminium saildrive housing with stainless components fixed to it. So there is nothing to set up a galvanic cell. A sacrificial anode is used in the two examples to protect the lower potential metal (the zinc in the yellow metal or the aluminium) from depletion by the higher. The anode has to be connected to the 2 metals immersed in the electrolyte (seawater) and position closely so that it can be "seen".

There was a time when boats were festooned with anodes because they were deemed a "good thing" but largely unnecessary. Look at modern boats which often have 10 or more through hulls and the only anodes you will see are connected to the sterngear or saildrive, plus possibly another that is the ground for the 240v circuit.

 

[vyv_cox]

That surprises me.

Tranona's post is spot on, but in addition it is not possible to protect fittings on two sides of the hull with one anode. An anode needs to 'see' the object it is protecting and ideally be close to it. If it was necessary to protect skin fittings and valves with anodes they would need one per fitting. A good copper alloy, bronze or DZR, needs no protection whatsoever and even standard 60/40 brass fittings, with which most boats were fitted until quite recently, lasted for many years without significant corrosion.

 

[Buck Turgidson]

Just to add to the above, my boat has her original Blakes bronze through hulls. Non are connected to the anode, all are as good as new. They are 52 years old.

 

[Frayed Knot]

Should not be a surprise if you understand the process of galvanic action in seawater.

Who said I understand it?
Thanks for your advice though - and Vyv - I may now do it differently but would still appreciate it if anyone can help with the original question

 

[john_morris_uk]

Who said I understand it?
Thanks for your advice though - and Vyv - I may now do it differently but would still appreciate it if anyone can help with the original question

Replace the gate valve with a bronze or DZR ball valve.

 

[zoidberg]

And you REALLY don’t need to connect metal through hulls etc to your cathodic protection.

Thanks to The Bish, and Mr T.

Yet another example of me blundering about not knowing what I am doing, so now I can remove some more unnecessary weight from my wee boat!

 

[ean_p]

The Tru Design answer to your need its on page 25 of their catalogue... Tru Design
The 90* Female -male Threaded connector

 

[lustyd]

For cockpit drains have you considered just not having a valve? If they’re needed to drain the cockpit there is no reason to ever close them and every reason to keep them open. Ideally the through hull should then be above the waterline in which case you can use the white TruDesign through hulls that connect directly to a hose.

 

[Tranona]

The Tru Design answer to your need its on page 25 of their catalogue... Tru Design
The 90* Female -male Threaded connector

But not the same size as the ones the OP has.

 

[Tranona]

For cockpit drains have you considered just not having a valve? If they’re needed to drain the cockpit there is no reason to ever close them and every reason to keep them open. Ideally the through hull should then be above the waterline in which case you can use the white TruDesign through hulls that connect directly to a hose.

They are not cockpit drains but deck drains that exit below the waterline. That is why they have to be as they are.

 

[Tranona]

Who said I understand it?
Thanks for your advice though - and Vyv - I may now do it differently but would still appreciate it if anyone can help with the original question

Pretty sure there is not a non metallic product to do your job - nor is there any need for one. If they have been in place for 40 years then really no need to change except get rid of the gate valve (and no need to double clip for exactly the same reason). Good quality 316 clips like that simply do not fail. If you took the clips off nothing would happen anyway. There is no stress, no pressure and almost certainly you will have to cut the hose off the spigot. Double clipping is an old wives tale, but manufacturers love it because they sell two clips when only one is needed. Would be a pretty poor product if it was so prone to failure that every one needs a back up which itself has the same chance of failing. Look under the bonnet of your car and you will not see any double clips even though the hoses contain fluid that is usually hot and under pressure.

I know you will ignore my advice on this because your surveyor will insist on double clipping. I did the same much as it offends me but in our mad world old wives tales repeated regularly seem to trump logic and evidence.

 

[lustyd]

They are not cockpit drains but deck drains that exit below the waterline. That is why they have to be as they are.

If that's the case I'd glass over them and either move above the waterline or just not have deck drains. Decks are self draining as a general rule, cockpits only need drains because they are enclosed. Had I kept my old boat I was going to glass in some pipe to remove all the failure points, that's also an option.

 

[Frayed Knot]

The Tru Design answer to your need its on page 25 of their catalogue... Tru Design
The 90* Female -male Threaded connector

Thanks for that. I’ll phone around tomorrow and see if anyone can supply them as nobody I’ve found actually lists them. Lee San seem to have the largest range available so I’ll try there first.

 

[Frayed Knot]

Pretty sure there is not a non metallic product to do your job - nor is there any need for one. If they have been in place for 40 years then really no need to change except get rid of the gate valve (and no need to double clip for exactly the same reason). Good quality 316 clips like that simply do not fail. If you took the clips off nothing would happen anyway. There is no stress, no pressure and almost certainly you will have to cut the hose off the spigot. Double clipping is an old wives tale, but manufacturers love it because they sell two clips when only one is needed. Would be a pretty poor product if it was so prone to failure that every one needs a back up which itself has the same chance of failing. Look under the bonnet of your car and you will not see any double clips even though the hoses contain fluid that is usually hot and under pressure.

I know you will ignore my advice on this because your surveyor will insist on double clipping. I did the same much as it offends me but in our mad world old wives tales repeated regularly seem to trump logic and evidence.

All good advice, thanks. And yes, I will ignore it! I agree totally re the double clipping but as you say: the surveyor said it, so if anything went seriously wrong I would be in breach of my insurance terms for the sake of about two quid…
Just a thought; if I were to simply replace the gate valve with a DZR ball valve & if you are correct that the elbow is bronze (I think you probably are) would that constitute dissimilar metals in contact?