Holding tank ventilator

[rog]

I would appreciate some advice.
A copper plumbers type pipe coming out the top of my holding tank has rotted through and come apart; it's probably as old as the boat which is about 7 years. There is a flexi plastic pipe attached which disappears into the boat and I can only assume it's purpose is to ventilate the tank.
From the look of it, I'd guess the tank must be steel or are they normally GRP or plastic - anyway it's covered in a layer of some hard white sorta material.

Assuming ventilation's required (per the infamous exploding toilet incident) and that's the purpose of this pipe, can I just seal the old pipe, drill through the white coating into the tank and fit a new, plastic plumbing outlet - seems it should be easy but I'm naturally suspicious especially as it's on a boat!
And why's the original copper which anyway seems to have almost blocked up with horrible black gunge!
Alternatively - where can I find out more?
Thanks in anticipation
Roger

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[oldsaltoz]

G'day rog,

I think I would drill out the copper pipe fitting and adapt it to a plastic line, the location of the vent outlet may be critical and relocation may cause a problem.

You could PM the 'headmistress' she will know for sure.

Good luck and avagoodweekend.........

<hr width=100% size=1> Old Salt Oz /forums/images/icons/cool.gif Growing old is unavoidable. However, growing up is still optional.

 

[Talbot]

Very very unlikely that the holding tank is metal, and if it is, replace it. Urine will rot the metal.

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[snowleopard]

the air you displace when you pump waste into the tank has to go somewhere, also air has to get in when you pump out.

the air from this outlet is VERY smelly so it needs a charcoal filter or you'll need a clothespeg every time you pump. your pipe should lead to a filter somewhere close to deck level and from there to a skin fitting lower down.

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[HeadMistress]

I've been away at the Annapolis boat show for the past week, so just seeing this...

All holding tanks MUST be vented to the outside of the boat...for two reasons: methane is flammable...and...air displaced by incoming waste must have an escape--or the tank pressurizes...air must also replace waste as it's pumped out, or the pump will pull a vacuum, making it impossible to pull any waste out of the tank--and can result in a cracked tank from a blocked vent if the suction is strong.

Minimum vent size is 1/2"...the larger diameter the better, however, because the key to odor elimination is oxygen--plenty of ventilation to the tank contents.

No metal of any kind should be used for holding tanks or sanitation plumbing...urine is so corrosive that it will eat through it in a few years (as is demonstrated by the condition of your copper pipe). All sanitation plumbing should be hose rated for sanitation...all connections double clamped.

How to install a new vent depends on the material your tank is made of...if GRP, a new hole and barbed fitting can be caulked. However, if the tank is plastic (polyethylene), no sealant, glue or caulk will bond to it permanently, so other means must be used to install or relocated fittings (which I'll be glad to describe if requested...but it doesn't appear to be the case here).

<hr width=100% size=1>Peggie Hall
Specializing in marine sanitation since 1987