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Old 15-03-2020, 19:13   #1
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Particle filter before or after the grease trap

Hi all,

Iím stuck in a logical stalemate. I can construct a logic for putting the particle filter either before or after the grease trap on my galley sink.

Regulations here require that I have both devices, so which order would you put them in, and why?

Matt
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Old 15-03-2020, 19:29   #2
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Re: Particle filter before or after the grease trap

I reckon it would depend on the type (construction) of the grease trap but in general, you don't grease in your particle filter. It doesn't matter so much if there is some particles caught in the grease trap.

Therefore grease trap first and then particle filter!

Off- topic: is this some SA reg? I have never heard of it elsewhere; although that doesn't mean much, there is presumably a lot of stuff I have never heard about!
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Old 15-03-2020, 20:47   #3
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Particle filter before or after the grease trap

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Originally Posted by Wotname View Post
I reckon it would depend on the type (construction) of the grease trap but in general, you don't grease in your particle filter. It doesn't matter so much if there is some particles caught in the grease trap.

Therefore grease trap first and then particle filter!

Off- topic: is this some SA reg? I have never heard of it elsewhere; although that doesn't mean much, there is presumably a lot of stuff I have never heard about!


Thanks Wottie, thatís one vote for that config.

Grease trap is a DIY contraption made from 100 mm PVC pipe, a T piece with screw caps at the top for cleaning and a bit of 40 mm high pressure PVC pipe to pick up water from the bottom of the trap to go overboard.

It comes from a careful reading of some EPA regs posted at our marina that state you may discharge grey water over the side if you meet a few criteria, including an inability to have a grey water tank plus an effective grease trap and particle filter. The boatís age ticks the first box, I can tick the other two.

Not sure if the regulation is local or Australia-wide. Pretty sure EPA is all-of-country for this stuff. (Edit: turns out I am wrong, itís state by state.)

I still want a way of holding small amounts of grey water if I can figure it out. I thought had it sorted a while back but that idea failed the practical maintenance test.
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Old 15-03-2020, 20:56   #4
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Particle filter before or after the grease trap

Hmmm... a follow up to this suggests it is different from state to state, and mostly is seems everywhere else I am planning to travel is pretty much unrestricted when it comes to grey water.

Meanwhile, I cannot find the flow chart online that is posted at our marina, so will see if can find out where it was obtained. It has the EPA logo on it, but no URL or other metadata. This is a worry, because what I can find from the South Australian EPA site suggests that the system I am proposing may not be acceptable as it will not have been officially certified.

Iíll keep building it though, because it is better than the apparently zero requirements of NSW and Tasmania.
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Old 15-03-2020, 21:12   #5
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Re: Particle filter before or after the grease trap

Because I suddenly find myself cooped-up with more time on my hands then I expected...

Is this the flowchart?



https://www.epa.sa.gov.au/files/14134_slide1.jpg

The slide is buried on this more general page, you have to expand the marine waters section.

https://www.epa.sa.gov.au/environmen...ater_discharge
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Old 15-03-2020, 21:30   #6
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Re: Particle filter before or after the grease trap

Every state is different...

South Australia https://www.epa.sa.gov.au/files/4774...wastewater.pdf (This seems to support the flowchart at our marina)

Tasmania https://epa.tas.gov.au/Documents/Boa...ct%20Sheet.pdf
(Note no requirement to treat grey water!)

NSW https://www.rms.nsw.gov.au/about/env...greywater.html
No grey water requirement for recreational vessels!

QLD https://www.msq.qld.gov.au/Marine-pollution/Sewage.aspx

A bit unclear, but appears to disregard grey water.
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Old 15-03-2020, 21:31   #7
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Re: Particle filter before or after the grease trap

Quote:
Originally Posted by Dsanduril View Post
Because I suddenly find myself cooped-up with more time on my hands then I expected...

Is this the flowchart?



https://www.epa.sa.gov.au/files/14134_slide1.jpg

The slide is buried on this more general page, you have to expand the marine waters section.

https://www.epa.sa.gov.au/environmen...ater_discharge


You truly are a google-Jedi! Thatís the one. Thank you.
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Old 15-03-2020, 21:34   #8
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Re: Particle filter before or after the grease trap

As can be seen, it becomes a grey area (pun unintended) about whether the vessel is capable of supporting a grey water treatment system.

Itís not an argument Iíd like to have with the EPA, so for the time being Iíll keep doing my dishes in the marina kitchen and showering in the marina showers, but Iíd put up a pretty strong argument that itís a least beyond my abilities or those of my wallet for this boat to fit a treatment system.
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Old 15-03-2020, 21:44   #9
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Re: Particle filter before or after the grease trap

Quote:
Originally Posted by GILow View Post
Hmmm... a follow up to this suggests it is different from state to state, and mostly is seems everywhere else I am planning to travel is pretty much unrestricted when it comes to grey water.

Meanwhile, I cannot find the flow chart online that is posted at our marina, so will see if can find out where it was obtained. It has the EPA logo on it, but no URL or other metadata. This is a worry, because what I can find from the South Australian EPA site suggests that the system I am proposing may not be acceptable as it will not have been officially certified.

Iíll keep building it though, because it is better than the apparently zero requirements of NSW and Tasmania.

You really need a copy of AS 4995.


At first glance, I would think your boat is big enough to support a holding tank, but the requirements of the standard could be anything. The only equipment manufacture I can see listed uses DAF, which is far more complex than what you have in mind.



I'm guessing you need to tank it.
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Old 16-03-2020, 01:02   #10
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Re: Particle filter before or after the grease trap

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You really need a copy of AS 4995.


At first glance, I would think your boat is big enough to support a holding tank, but the requirements of the standard could be anything. The only equipment manufacture I can see listed uses DAF, which is far more complex than what you have in mind.



I'm guessing you need to tank it.


If I were staying in South Australia you may be right. Though, interestingly, gossip around the marina is that the EPA recommended my proposed setup to a guy on a Roberts 45, which is a much bigger boat than mine.

Thankfully Iíll be gone from SA in a month, and the places I am going are strangely lenient about grey water.

Iíll still put this system in place, simply because I think it is the right thing to do.

So I still have to figure out the best order of components.
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Old 16-03-2020, 06:28   #11
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Re: Particle filter before or after the grease trap

If it were me, I'd filter particles first and then capture grease, which is also easier to control on the front end so cleaning should be less frequent. You're likely to have easier access to the inline filter trap if you put it first. But that's just the way I'd thought process it. I have no direct experience so take that for what it's worth.
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Old 16-03-2020, 07:09   #12
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Re: Particle filter before or after the grease trap

Quote:
Originally Posted by GILow View Post
If I were staying in South Australia you may be right. Though, interestingly, gossip around the marina is that the EPA recommended my proposed setup to a guy on a Roberts 45, which is a much bigger boat than mine.

Thankfully Iíll be gone from SA in a month, and the places I am going are strangely lenient about grey water.

Iíll still put this system in place, simply because I think it is the right thing to do.

So I still have to figure out the best order of components.

Makes sense.


I design industrial scale traps, so if you post a sketch I'd be glad to comment.


In this case the strainers go first, since some food scraps are gravity neutral and will interfere with grease separation. 1/8" mesh should be fine enough.
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Old 16-03-2020, 13:59   #13
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Re: Particle filter before or after the grease trap

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Makes sense.


I design industrial scale traps, so if you post a sketch I'd be glad to comment.


In this case the strainers go first, since some food scraps are gravity neutral and will interfere with grease separation. 1/8" mesh should be fine enough.


Thank you, Iíd appreciate your feedback.

Logic of the design is that I should be able to flush it by shutting off the seacock, opening the screw cap on the T arm and then releasing water into it from the sink which should float the top layer of grease out into a carefully placed bucket.

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Old 16-03-2020, 14:30   #14
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Re: Particle filter before or after the grease trap

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Originally Posted by GILow View Post
Thank you, Iíd appreciate your feedback.

Logic of the design is that I should be able to flush it by shutting off the seacock, opening the screw cap on the T arm and then releasing water into it from the sink which should float the top layer of grease out into a carefully placed bucket.

Attachment 210684

Thanks for posting that! A few thoughts that I'm pretty sure of, based on experience.
  • The particle filter goes before the grease trap. Just a chunk catcher. If this is just for your saticfaction, a screen in the sink will work well. Otherwise, something in-line, easy to clean, no smaller than 3/16" holes (or it will clog constantly).
  • The inlet should go below the water surface ~ 2 inches and end in a Tee. This prevents the falling water from entraining the grease back into the water. VERY IMPORTANT and a common mistake.
  • The exit should not be on the bottom (about 1/2 way or 2/3 down). There will be sludge. But maybe not much.
  • Floating the oil off is clever. I like that. But you will also need a way to remove sludge periodically. Perhaps a small valve in the bottom to drain, and then a way to remove it.
  • Remember that you need a P-trap to keep gasses out of the sink. This will smell.
  • Without a vent (the P-trap will block that) this becomes like a holding tank. Gasses that generate will find a place to go. They will either push into the sink or push water and grease out the discharge.
  • Typically you need at least 20 minutes settling time for separation. It depends how good a job you want to do. Constant flow through, not as good, but the Tee at the inlet will help. Remember that the grease bubbles must rise faster than the water down flow rate or they can't buck the tide.
Good luck! It's nice to see people that try.
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Old 16-03-2020, 14:54   #15
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Re: Particle filter before or after the grease trap

My Marina in Vic is in a national park and a very high conservation area,
On the gate is two signs, No dogs or discharging toilets overboard while in the Marina,
There is nothing on the sinks being discharged overboard that I have seen,,

In my RV, I can discharge my grey tanks any where,
But the Black tank must be into a Regulated discharge point, Which most towns now have, Dump Point,
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