poly holding tank life expectancy?

[jimbojonesbos]

What is the life expectancy of a poly holding tank? My 37 year old boat has the original Kracor (I think) holding tank and while I am replacing all the associated smelly plumbing it occurs to me that maybe the safe bet is to install a new tank while it is all apart. Much googling has turned nothing up other than some industrial tank distributors who state 15-20 years for chemical storage.

I have only ever owned old boats and all my previous boats had no holding tank when I bought them so I have always started with a new system. The current system has nasty smelly cheap hoses but the tank has no obvious signs of failure. But I don't want to put all new hoses and hardware in only to have the tank fail and make a mess.



Any thoughts or links to reputable sources?
Thanks!

[sailorboy1]

I believe that unless you damage it, the tank will last basically forever.

[peghall]

Unless a blocked vent or an over-tightened fitting causes a tank to split or crack, a PE tank can last as long as the boat lasts. Kracor tank walls are only 1/4" thick, but are decent quality, so as long as the bottom and sides are well supported and you don't see any indication of a crack, I'd keep it.

If you find you need to replace it, Ronco Plastics (no relation to the VegoMatic Ronco) Ronco Plastics marine Tanks is your best source for a tank. They make TOP quality thick-walled (at least 3/8") water and waste tanks for a very reasonable price and have more than 400 shapes and sizes, over 100 of which are non-rectangular, and they install fittings in the sizes and locations specified by the customer when they make the tank. And they sell direct.

Whether you keep the Kracor or replace it, be be careful not to over-tighten the thread-barb hose fittings. Do not use any sealant, just wrap threads in a teflon tape and tighten no more than one turn past hand tight, plus enough to aim a 90 where it needs to go.

As for hose...I'd go with Raritan SaniFlex Raritan SaniFlex hose In the 10 years it's been on the market it's proven to be 100% odor-permeation resistant and has the added advantage of being so flexible it can be bent like a hairpin without kinking. Defender has it for <$10'ft.

What's the make/model/age of the toilet? Depending on your answer, it may be time--even past time--to replace it.

--Peggie

[jimbojonesbos]

Thanks Peggie I actually bought your book this summer. The head is a Raritan PHII,I suspect it is original to the boat but I am not sure. I've had good luck with that model so I don't plan on ditching it although I will either rebuild it or replace the pump assembly this Spring for sure.



The existing hose is all the cheap vinyl stuff, I have a roll of Raritan saniflex and I planned on using that along with some PVC as appropriate. I've been waiting for cold weather to pull everything out. The boat had been sitting for a number of years before I bought it and smelled horrific. I got the stank down with a few fresh water flushes/ pumpouts and K.O. but the hoses are all saturated.


Thanks for the advice on the tank that will save me a few boatbucks for sure

[peghall]

Originally Posted by jimbojonesbos

Thanks Peggie I actually bought your book this summer. The head is a Raritan PHII,I suspect it is original to the boat but I am not sure. I've had good luck with that model so I don't plan on ditching it although I will either rebuild it or replace the pump assembly this Spring for sure.

The rebuild kit is only about $60, so I'd try rebuilding it first. Be sure you get the right kit, 'cuz there are two, depending on when it was built and they aren't interchangeable... PHIIRK is the kit for those made before 6/92...PHIIRKC is the one for those made after 6/92. If you aren't sure of its age, find the serial # on the pump and call Raritan tech support 800-352-5630.


I'm always glad to help or answer questions, either here or directly.


--Peggie

[01kiwijohn]

Physical damage excepted, it should outlast both you and the boat.

[Cabo Jim]

What about odor? Does the plastic of the holding tank permeate odor as bad as rubber hose?

[David M]

HDPE? Until the sun expands towards the end of it's life and absorbs the Earth.

[peghall]

No...it's almost unheard of for PE (and btw, water and waste tanks are all LDPE) to permeate. I've only heard of one instance in the 30 years I've spent in marine sanitation and the tank mfr admitted it only due to faulty curing.


--Peggie

[Bill Seal]

How would a custom holding tank laid up from fiberglass/polyester about 3/16" or 1/4" work out?

[01kiwijohn]

I've never encountered a case of a holding tank permeability. The couple of times of such alleged complaints have been resolved by tightening the hose clamps a bit. Oftentimes, a clamp may need to be re-torqued after settling in. Good hose costs around $10 per foot so it is tempting to cut corners here; DON'T do that.

[01kiwijohn]

It'll work OK if you are meticulous about the construction, fitting installation and fiber-glassing. I made one, to fit into the bow of a Martin 29, and after 10 years or so it was still doing the job. I've since lost track of the boat so can't verify more than that.

[Doublet]

Smells from the toilet? Do not forget the tank vent. Many boat owners do. Do not vent into the forward anchor locker. That is disasterous at anchor. Vent to the aft most point on the boat. Always use the best hose or pipe you can get that is non-permeable and make sure that after the first high point, it slopes downhill all the way to the exit point. This will stop any water lock that might occur and avoid any build up of pressure in the holding tank. It only needs a slight pressure over a long period to permeate smell. I did my full installation some 20 years ago and have had no troubles or odor since. My tank is PE.

[peghall]

I'm sorry, but I have to disagree with everything you said except "do not vent into the forward anchor locker." To do so would be illegal in the US. USCG regs require that all waste tanks--black water and gray water--be vented to the outside of the boat.

However, while there's nothing illegal about venting to the aftmost point on the boat, that guarantees that what comes out the vent will stink...so while you're keeping the odor away from those onboard your boat, those downwind of your boat won't appreciate it.

Odor out the vent can actually be prevented by vented to provide sufficient oxygen (fresh air) to the tank. I didn't invent anything new here...you just need to apply the laws of bio-physics 101: when organic material breaks down AEROBICALLY (oxygenated), it generates CO2 which is odorless. It's only when organic materal breaks down ANAEROBICALLY (without oxygen), it generates gasses that are not only stinky, but also toxic and flammable--sulfur dioxide and hydrogen sulfide.

So ideally you want the vent line to be as as short and straight as possible and also to be at least 1" in diameter to provide a good path for fresh air to exchange with the gasses in the tank.

If you're interested in learning more about this, it's all explained in detail in my book (see link in my signature..except you'd want to use amazon.au). I'm always glad to answer questions whether you buy the book or not.


--Peggie

[a64pilot]

Originally Posted by Bill Seal

How would a custom holding tank laid up from fiberglass/polyester about 3/16" or 1/4" work out?

Don’t, send these people a drawing or I guess your old tank if you can’t do a drawing and they will make it exactly to specs.
I added another 2.5” bung for a macerator and increased my vent tube of 1” and they of course put all the bungs in.
http://triplemplastics.us/#&panel1-2

Mom and Pop shop I think, but they do good work, on time and priced as quoted.