Holding tank pipe from heads

[Fenders]

I recently noticed some corrosion on the metal elbow that is located on the top of the holding tank. It is connected to a hose that comes from the heads.
I am considering replacing this metal elbow but I see that it appears to be integral to the plastic tank.
Is it possible to remove this or is it a case of buying a new tank complete with fittings.
I'd hate to have the experience of one of this forum's contributors who described his "exploding tank", which I think may have been  caused by a blockage.

The boat is a 2004 B32.

Thanks

[Yngmar]

We have a similar elbow on the bottom of our holding tank. It's simply a threaded elbow with a nut on the inside retaining it. Technically accessible via the inspection hatch, but practically you'll need a bloody long extension to get at the nut.

[Symphony]

Would not worry too much about that surface deposit. Probably a slight leakage has caused it and it is salt deposits rather than corrosion of the metal. Clean it up, check all the connections and keep an eye on it.

[Salty]

Would not worry too much about that surface deposit. Probably a slight leakage has caused it and it is salt deposits rather than corrosion of the metal. Clean it up, check all the connections and keep an eye on it.

Quite agree, also it looks like the elbow is made of bronze so the corrosion is not rust as such and I doubt if it’s due to leakage through the metal. More likely either leakage through from a deck fitting above, or from condensation dripping off a low point, particularly if you spent time onboard during the winter and had a heater running. Suggest you try the blue tissue paper trick and suspend a sheet of the stuff horizontally above the area but not in contact with it and see if the paper gets wet.

[Fenders]

Thanks for all your replies.
They have given me some direction regarding the cause of the corrosion.
The elbow does look like a bronze fitting. Strangely enough above the holding tank I have some clips where I store a deck brush and a sponge mop. The heads of these hang directly over the holding tank and maybe over a long period of time water has dripped from the brush and mop onto the top of the holding tank and elbow.

I was on the boat today and used a small piece of wet and dry on the corrosion. The corrosion appears to be only on the surface so that would suggest to me that the cause is not internal.

I will keep a close eye on it just in case.

Thanks again for your guidance

Fenders