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#11 Frank

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Posted 03 July 2019 - 02:53 PM

for what it is worth on the aircraft lav plumbing we use Acetic acid same as what you find in Vinegar.


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#12 Knot Me... maybe

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Posted 03 July 2019 - 02:56 PM

I built a plywood holding tank with about a million coats of epoxy on it last year. Might be exagerating on the number of coats ;-)

That's good to hear, I did similar and have been wondering.

 

But I only did 999,991 coats less then you ;)

Ply, resin, resin, resin purple bog slurry, resin, resin fawn bog slurry, resin, flowcoat, flowcoat, flowcoat, fingers tightly crossed.

 

Are you getting build up of something/anything in your ply tank?

 

I can take the lid off mine, after a lot of screws and slicing thru 25mm wide MS seal (which may mean it's a chainsaw off, I hope not) but I'm really not wanting too.


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#13 Terry B

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Posted 03 July 2019 - 03:45 PM

KM, I just used epoxy coats, nothing else. I saw some things John Wellsford had written about making these and he reckoned just epoxy was fine.

I was going to put a removable lid on it but in the end I sealed it all up. Couldn't stand the thought of leaks - waste or smell! Can't see inside at all!!

I have relatively straight inlet & outlet hoses to the tank so should be (yeah right) simple to clear any blockages without disassembling everything.

I slanted the bottom of the tank toward the outlet pipe so (hopefully) it empties completely when flushed with fresh water. Which I do every time I'm back in the slip.

Worst comes to worst - i build a new one from scrap plywood again in 5 years or so.........or slice the top off with a skilsaw or on the table saw, clean it up and epoxy it back together.

 

So far, I'm very pleased.

I only built one myself as the space was small and awkward and I would have only got a 15L version of the plastic ones into the space. I now have 32L capacity.


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TERRY

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#14 Knot Me... maybe

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Posted 03 July 2019 - 04:06 PM

Loving that post Thanks Terry.

 

Mine sounds like yours with carefully positioned plumbing, sloping floor etc. I have a vent directly over the outlet, the theory being if we experiance some contents reluctant to leave then I can whip the vent off and get a bit of wire in there for encouragement. I went with the slurry to give some film thickness thinking thicker is harder for stinky to get through.

 

The one concern I have is I have flush thru hulls so pipes come into those then there is a 90 degree corner before exiting. I hope 'thing's will get around that corner OK.

 

And tell me about building one in in such a cozy space, would be easy for a small Chinese contortionist but knot for this lad. I also build a good size one due to lack of options to put in a tiny plastic one. I've got probably 25-30lts. 

 

Phewwwwww.... I've had some concerns over that but much happier now after hearing those bits from Terry. That tank was 1 of 3 concerns I have from the big tweak so now down to 2.


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#15 vic008

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Posted 03 July 2019 - 05:15 PM

Hoping you find big enough, mine at 30L, wishing it was bigger.Really only for emergency use anyway. Big advocate for a level gauge- you really need to know the level.Bought an Amazon portable,thru plastic,etc but while works on the kettle no good on tank.
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#16 Terry B

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Posted 03 July 2019 - 06:08 PM

Vic - because I can't 'see' the tank level, I'm going to work out how many pumps to a full tank  :) Will do this in spring when I next have at least a 3-4 day trip. That way I can get a rough idea of toilet visits per tank - at least on average anyway.

Everyone on board has to write down number of pumps each time it's used - hopefully I can work out roughly when it's getting close to full that way. 

 

Careful eye on the vent overflowing........... ;-)  Cabin boys task, that..........

 

Might also be a sh:)storm.............. :wtf:

 

I normally sail solo or 2 up. Rarely more than that, so with 'judicious' use, 32L should be fine. Ain't got more room for a larger tank unless I do major surgery and I'm not going to do that.

 

And KM - hopefully my novice tank building doesn't give you a false sense of security!

Before building it, I did talk to lottsa people and google was my friend.

As was Brian (a plug for Burnsco here) at Burnsco who's advice was brilliant. Staff got a dozen beer as reward.

Also, a mate built one out of ply with only epoxy on it and it has happily worked for around 7 years now with no issues - and they use the boat a lot.

 

Cheers.


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TERRY

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#17 ynot

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Posted 03 July 2019 - 07:39 PM

Remember in theory the vent should be as big as the inlet.
This allows air to flow in and out through the same hole which let's things and stuff work right and apparently let's micro things do their stuff. (in a septic tank anyway but in a yacht probably does not sit long enough to let them do Thier stuff)
Well designed waste tanks will not smell.
However in a yacht a 38mm vent pipe probably is not what most people are willing to do.
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#18 Knot Me... maybe

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Posted 03 July 2019 - 08:14 PM

And KM - hopefully my novice tank building doesn't give you a false sense of security!

After 7 years and you're still OK, I'll take that quite happily at the moment.

 

 

Remember in theory the vent should be as big as the inlet

I didn't have one in there but put one in, about 12mm. I also put a value in it so I can close it off if I like. 

The theory being if things get a bit stuck in the system I can close the vent and pressurise it all, then bang to outlet open and hopefully things will fire out not unlike a sub launching a cruise missile. In testing I can get quite a loot of pressure in there so we'll see. I did build it with that theory in mind so again we'll see.


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#19 marinheiro

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Posted 03 July 2019 - 08:27 PM

Vic - because I can't 'see' the tank level, I'm going to work out how many pumps to a full tank   :) Will do this in spring when I next have at least a 3-4 day trip. That way I can get a rough idea of toilet visits per tank - at least on average anyway.

Everyone on board has to write down number of pumps each time it's used - hopefully I can work out roughly when it's getting close to full that way. 

 

If you want to "double" the tank capacity, have a separate bin for loo paper. 


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#20 Dtwo

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Posted 04 July 2019 - 08:59 AM

One of the most important things with holding tanks is to lose the wire mesh from the breather vent.  If you have repeated overfill "events", bog paper does a papier mache trick and blocks the vent, creating the ultimate shitstorm.  How do I know that?


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