Fitting cheapish PVC valves on WCs, am I missing something

[MapisM]

Each of my WC outlets go to a 3-way valve, that gives the choice of dumping either to the waste tank or straight to the sea (with an additional valve attached to the thru-hull fitting).
In one of these piping arrangements, both the 3-way valve and the other one on the thru-hull fitting are very hard to operate, sure enough due to some corrosion on the metal ball inside them.

Now, rather than replacing them some other metal valves, a thought popped to my mind: wouldn't plain vanilla PVC work equally well, and probably be more longlasting? I mean, even without considering exotic Marelon stuff, wouldn't basic PVC valves sold in any garden center be more than good enough for this job?
After all, the pressure they must withstand is tiny, they are placed in a hidden location where the risk that something hits and possibly damage/crack them is zero, and also the temperature excursion is nowhere near the one of the e/r. Besides, there's absolutely no sun exposure at all.
Otoh, the liquid they must deal with (either salt water or the other stuff coming from the WC, mixed with fresh water) should be less aggressive towards PVC rather than metal, I reckon.

So, over to you folks, what am I missing, if anything? TIA!

 

[jfm]

I always use plastic upstream of the bronze thru hull and seacocks, for the reasons you say. I have never used garden centre €5 things because I don't recall seeing them with 1.5 inch hose tails. I have only seen them with 1.5inch compression fittings. Quality wise I expect they are good (I use them for garden irrigation) but I prefer the ones in this link and always use them on thr boat. https://www.asap-supplies.com/fittings-valves-strainers/valves-spares/diverter-valves

 

[Boat2016]

I have had the Whale valves as in the above link and can recommend them for their quality, what i liked is you can also easily dismantle to clear a blockage.

 

[vas]

fwiw,
I have used 1.5+ inch irrigation components in the engine freshwater flushing, but that was straight components.
I did use Trudesign 3-way valves for swapping from strainer to freshwater though.

One word of caution (BTW I'D NEVER do it) is that the irrigation stuff may be OK, but IF you ever thinking of dismantling them to clean or whatever just forget it. I mean it's dead easy to take apart but IMPOSSIBLE to refit without it ending up leaking (and it's OK in freshwater but not too sure I'd like that on waste...) Annoyed, went back to the guys I bought them and they explained that even they don't touch them, just replace them if they have to do something. Cheap as chips they are, but imho not for sewage!

V.

 

[Andy Cox]

Mapis, one other thought would be the insurance implications if for some reason the garden centre pipe work failed in some way and allowed water ingress.

Just my two pennies worth.......

Andy

 

[MapisM]

Thanks everybody, good to hear that my train of thought made sense.

I always use plastic upstream of the bronze thru hull and seacocks, for the reasons you say.

Just another question: for this particular application, I was thinking that it could make sense to use plastic also for the seacock.
I mean, at the moment I've got a bronze through hull fitting which is still as good as new, so obviously that's going to stay.
But I can't think of any serious reason for not using plastic for both the 3-ways diverter and the seacock.

Btw, in the existing arrangement (which I would keep), the 3-ways valve is directly connected to a bronze curve, which is also directly connected to the seacock.
Therefore, either the seacock or the 3-ways valve can both be used to shut sea water ingress, in case of failure of any hoses upstream.
A simultaneous failure of both seems pretty unlikely to me.
Otoh, a broken or cracked seacock would still be problematic, of course - and in this sense I can see why a stronger material is preferable.
Then again, we're talking of a smallish valve, not exposed to any possible impact...

 

[MapisM]

Mapis, one other thought would be the insurance implications if for some reason the garden centre pipe work failed in some way and allowed water ingress.

Mmm... That's a good enough point in favour of bronze for the seacock, I reckon.
Out of curiosity, do you folks see also any technical reasons?

 

[Portofino]

Mmm... That's a good enough point in favour of bronze for the seacock, I reckon.
Out of curiosity, do you folks see also any technical reasons?

We had a plastic 3 way like one in the pics JFM linked in our Sunseeker.
After a while the o ring to the handle started to weep and there’s a rubber gasket exposed at the edges .
There always was an odour of sorts .
I dismantled it once to find a brown hard scale reducing the dia .

I would stick with metal OEM , no continuity to the exterior via gaskets for odours or dodgy o rings to eventually go .

The two metal ones on this boat feel superior and bomb proof .

 

[MapisM]

The two metal ones on this boat feel superior and bomb proof

Porto, do you possibly remember the type/brand of your 3-ways valves?
On my boat, they are chromed brass type, and if I'd stick with metal I'd rather replace that with bronze or at least DZR, but I've yet to find such materials in any 3-ways thingies.

 

[Portofino]

Porto, do you possibly remember the type/brand of your 3-ways valves?
On my boat, they are chromed brass type, and if I'd stick with metal I'd rather replace that with bronze or at least DZR, but I've yet to find such materials in any 3-ways thingies.

Best image I could get , a circle with 3 dots .
It came with the boat and was not party to the decision btw .

 

[MapisM]

Thanks PF, I've never seen that logo before, but it's not worth investigating further, because also that valve is definitely chromed brass, and also has an aluminum lever btw, which I've seen failing in the past, in bilge environments.
For some reason, nobody must have thought so far that 3-way valves can have their place also in applications requiring bronze or DZR...
I will follow-up here in case I will find something, but I'm not holding my breath.

 

[BartW]

You could check the 3way valves here in BA, but I’m afraid not dzr, they become sticking after years of no movement, but they have a steel lever, available from ceresoli iirc. I like the idea of the plastic valves.

 

[MapisM]

I like the idea of the plastic valves.

Yup, so do I.
In the meantime, the very latest news from the yard (good, for a change!) is that they managed to clean all the existing 3 ways WC valves, and now they look like brand new, and are working like a charm!
So, plastic valves are one thing that for now goes in the "to be considered for the future" folder! :encouragement: