Gravity Solids Trap before graywater tank?

[Inner Love]

Is there a screened solids trap I can install in my ABS DWV piping which has a drawer or other means of easily emptying the solids once it's full? It would be nice to be able to use the kitchen sink like in a house with a erator (garbage disposal) with a P-trap to stop smell coming back up from the drain.



I've thought about possible solutions to solids in graywater and decided it's better to catch the solids before they enter the gray tanks. I will be using two 360 degree loops consisting of tightest radius turns using 2" pipe for all greywater piping right before a solids trap. I am aware of the potential clogging potential with grease and settling solids in a double loop, which is why I want to mitigate that by having a bottom clean-out (like on some sink P-traps) and putting the double loop at the lowest point it can relative to the maximum level of the graywater tank. All DWV piping to the tanks will be given maximum slope given available space, and side to side runs that have to go above the frame rails will be kept as short as possible before dropping down. I'm designing to ideally not have any standing water in the pipes when my bus is on level ground, except for the double loop. For anyone wondering, my waste tanks will be vented through the floor and ceiling to end above the roof.



Having no solids in the gray tank means rarely needing to spray it out like with the blackwater tank, and I can use cheap 12v transfer pumps potentially without intake screening to transfer greywater through the black tank when it's dumping time.



I know there are possible solutions like products used in commercial kitchens and for other applications but I do not know the term(s) that is used for, so I haven't been able to google for products. I would like to use this thread to bounce ideas and potential solutions to trapping solids in a graywater stream before entering the tank.

 

[Rucker]

Google 'grease trap' and you'll see a whole bunch of products that solve this problem.

If I were doing this I'd probably build it rather than buy something.

 

[Jolly Roger bus 223]

also look at drum traps.

 

[Inner Love]

Is there some kind of canister strainer I can add after the drum trap? Or a drum trap with an integrated canister strainer? I don't want to have a strainerless drum trap only to have light particles enter the tank anyway.

If I were doing this I'd probably build it rather than buy something.

It's very hard to tell through pictures and videos if there is, or how effective a grease trap built-in strainer is. Thank you, I would have not thought of using a grease trap for a solids trap. I watched grease trap servicing videos on YouTube from septic and drain unclogging channels, so I have heard of a grease trap.



Given the available space above the maximum operational fill level inside the greywater tanks, and the already limited space for pipe slope, It's more than likely going to need to be a side access trap (the drum trap). To any aspiring inventors or entreprenuers reading this, this is a product improvement oppurtunity.



What I am looking for is a large version of a in-line water strainer, like https://www.amazon.com/SHURFLO-Trailer-Filter-Fresh-Strainer/dp/B01KR7AIP2 or https://www.amazon.com/Twinkle-Star-Sediment-Attachment-Pressure/dp/B081CN82MB. Ideally something with 2" or 3" slip or screw fittings, with a large cup shaped fine strainer mesh made of plastic or stainless steel. Something I could unscrew and wash out, and screw back in. If this isn't available, I will have to make one with pipe fittings.



I want my transfer & drain ports as low as physically possible on the greywater tanks, as a additional 1/4" water slice could mean half a gallon inside of a 50 gallon graywater tank. I am even thinking of adding in a pneumatic-powered vacuum pipe to get the last 1/4" of greywater out of the tank when it's discharge time.

 

[turf]

what are you smoking man?
maybe share that ****?
idk

instead of redesigning and inventing drain parts, why not just do it like others? is there really a need to recover those solids?

your sink strainer, is your solids strainer. if thats not good enough, stick a coffee filter in it.

your assumptions and decisions about your system just show that you've never camped and used the systems that are in place to deal with your waste.

a double loop the loop? seriously, wtf? on a gravity drain? really? why?

waste goes from your sink, to your waste tank. from your waste tank, it goes into an approved liquid waste disposal system.

instead of removing the solids, just make them flow better. use more water. use a bigger tank. any legal liquid disposal method can handle liquids/solids as long as it flows.

rinsing a tank is easy and part of my usual dump routine. i even think i got a video to share. lol

 

[turf]

picture story time

here is my tank.
here i am dumping my tank.
the hardware involved is a rinse elbow, a garden hose, and the rv sewer hose.

the elbow allows a hose to be hooked to the sewer hose.

after i dump the waste, i turn the elbow up and turn on the hose to refill the tank from the hose.
when the tank is full of rinse water to my liking, i turn the elbow back down and it rinses the tank down the rv sewer line.

i have disposable gloves to wear when i do this, but i rarely dawn them because i rarely need them. its a pretty clean process, unless there is an equipment failure. if that happens, i get the gloves, and i still got hose to wash everything into the dump...

rinse vid
https://photos.app.goo.gl/cJUQzYW3DL6zqa4MA
elbow up and down pics

 

[Mercuric Mind]

The best thing to do is to prevent the solid waste from going down the drain in the first place, or at least as much as possible. In addition I would treat your gray and black tanks with an enzyme drain cleaner like Bio-Ross. The stuff really reduced the volume of organic solids and reduces odor.

 

[Inner Love]

I am looking to save space under the kitchen sink as much as possible, as I will only have room for a 6’ kitchenette. I want to have all my cleaning products and parts (for all areas of living space, under the sink and I want the column in the way of accessing what is in the back of the cabinet to be an erator. I want to have an erator there instead of a p-trap and trap the solids below the floor.

Many of my decision are around the space available, including the double loop. Running a discharge hose under the bus to discharge the right side gray water tank is an inconvenience I can save with this system design. I have not used any of the systems I am designing yet, I am thinking about what are the pain points of using the system.

To strain everything down to the size of sand is what I expect to be able to do with a solids trap. Fine sediments and grease blobs will still enter the tank and should be able to flow through a transfer pump without problems. When driving to a dump site, the fine sediments and grease blobs will be in suspension from agitation and movement.

Instead of having a pile of stinky muck in the living space (regardless of where it is), I can instead have it in a underfloor solids trap, and handle it outside.

When it’s dumping time, I want to connect my drain hose to one tank (the black water) and turn on the transfer pumps. As the tanks are emptying I want to fill my freshwater (if available and allowed). I will still have a clean out port on each tank, used rarely with this design.

 

[Carrier6]

As a commercial plumbing contractor for 34 years I can tell you that you are digging a very problematic hole. The only way to stop the solids is a screen. That screen will need to be cleaned probably every time you use the sink. Waste in pipes don't flow the way you think. You will get food particles hanging on to the inside of the pipe for days before they flush out. A disposal is a terrible idea if you are concerned about solids in you tank. Also the disposal will not stop the sewer gas smell. That will only be solved by a Ptrap right under the basket strainer. We have an old rule about solids in the sink. If you can pick it up, throw it away in the garbage, if it's too small catch it in the sink basket strainer. Pipe sizing and grade are a huge deal when you start doing what you want to do. The grease in the system will plage you at every step. Any hot water you use in that sink will liquefy the grease and let it coat the pipes above the flow line of the pipe. It will clump off as you drive or just using the drains causing the screens to plug again. I don't even want to get to the double loops in the system, that is a total mistake. The biggest issue I think you are going to find is most of the smells you will get is from the system is in the pipe and fittings. This is why our codes restrict how long a drain line can be and how many changes of direction before the Ptrap.

Good luck with your build.

 

[Rucker]

I'm not sure I really understand your design goals. Are you trying to avoid having a gravity dump from your graywater tank?

I don't hear a lot of issues with graywater tanks.

Here are my other suggestions:
-make sure you have wet traps or hepflos at every drain to prevent sewer gases from coming into the bus;
-let the stuff build up, and make your holding tank removeable so you can give it a thorough cleaning every season (my tanks are pretty permanently installed and I wish I make them removeable for repair etc.);
-Don't let stuff go down the drain. A garbage disposal is probably the most efficient way to ensure some goopy sludge buildup. Especially grease.

In my experience, the only thing that goes down our drains is dish soap, toothpaste, and shampoo. It's just not an issue for us.

 

[Inner Love]

I am trying to avoid having to dump each tank individually, while not having solids in the greywater tanks.



I am looking to build a low maintence system without solids build up in the greywater tanks, with a single dump point (for routine dumping, access ports will be at the bottom of all tanks). I want both greywater tanks to be connected to dedicated transfer pumps or pneumatic driven venturi pump. I am really leaning to the pneumatic venturi pump as I can tap into my buses existing air brake system, and I don't need to worry about potentially running a transfer pump dry and has less cost and moving parts overall. I could make two venturi pumps easily with all PVC pipe, and route it into the blackwater tank. Choice of manual pneumatic valve or a water level sensor switch, a override switch, relay to a pneumatic servo switch. This videos shows a PVC venturi pump:

, and this video gives context to using compressed air for vacuuming:

.


I do want hepflows (one way flaps) in addition to wet traps.



If I could I would go to a commercial plumbing store and look at kitchen grease traps to see how and where to add mesh screens inside for solids catchment. What I am really looking for is to buy or make some kind of removable canister, like I described in post #4.

What I am looking for is a large version of a in-line water strainer, like https://www.amazon.com/SHURFLO-Trailer-Filter-Fresh-Strainer/dp/B01KR7AIP2 or https://www.amazon.com/Twinkle-Star-Sediment-Attachment-Pressure/dp/B081CN82MB. Ideally something with 2" or 3" slip or screw fittings, with a large cup shaped fine strainer mesh made of plastic or stainless steel. Something I could unscrew and wash out, and screw back in. If this isn't available, I will have to make one with pipe fittings.

I thought about letting the solids build up in the greywater tanks. I designed a 1" PVC pipe tree with a thousand pinholes which would be permanently installed and adhered onto the bottom of the greywater tanks with starboard blocks, and then connecting that to a transfer pump outside of the tank. I thought about putting the same type of sieve used to prevent solids entering in-ground drainage pipe, around all of the pipe. I discarded this design as eventually the sleeve would be completely blocked by mold growing in goopy sludge, lowering the flow over time before finally needing a difficult to do replacement.



I had this other idea of taking a 4 gallon square bucket and somehow adding multiple stacked removable screens inside of it, with a watertight bottom outlet that could be disconnected for bucket removal as to clean the bucket out.



It is good advice about the erator. I don't think I want an erator now.

 

[Inner Love]

After thinking about this problem, more web searches, and looking at solids interceptors on grainger.com stated to catch things larger than sand, I will have to compromise with my system.

I read this article and in it the person who was reusing kitchen greywater in the garden, tried every kind of filter and screen and after frequent clogs, switched to draining directly into a bed of wood chips outside their sticks and bricks home.
https://www.hachettebookgroup.com/s...er-water-conservation-straight-from-the-sink/

A reasonable compromise that meets my goal of dumping all tanks through a single outlet is to route all drains into one of the two greywater tanks, let the solids settle and accumulate in that tank, and design to overflow into the tank on the opposite side.

Much like a 2 compartment septic tank, the overflow outlet on the solids catching tank goes mid-level on the side of the tank, as to drain water above the grit and solids sitting on the bottom and below any floating scum later on the surface of the greywater. Unless driving on a dirt road with full tanks, the overflow pipe will not be catching many solids and can be screened without frequent clogs. The overflow pipe is meant to be a one-way pipe, so it will have a back flow preventer. The overflow pipe then inlets into the second greywater tank on the right side of my skoolie, with little to no solids or scum. The overflow pipe terminates on the side of the second greywater tank, positioned 3/4 of the way to the full level of it, to ensure gravity can fill the second greywater tank without the first tank over topping, even if the bus is parked on the left side of a unusually high crowned one-way street.



For the tranfer to the blackwater tank from the solids catching greywater tank at dumping time, I would construct an XL pneumatic powered venturi pump so most of the solids are sucked out each time I dump the blackwater tank.

 

[britpotato]

I like the Macgyver quality of your thinking. These conversations about "I want to do this weird thing that normally people don't do" is one of the things that makes skoolies really fun!

If the goal is being able to dump both a black water tank and a grey water tank by pouring grey into the black... You could put a valve on your black water tank vent and a dump gate on the inlet to the tank (from the toilet). Add a pipe with a one-way sanitary waste valve from your grey to your black (like this one: https://a.co/d/hWSxB2d). It needs to go from the bottom of your grey to the top of your black (which can be done with a pipe run inside all the way to the bottom, or directly out the bottom). The grey needs to be vented really well or things will rattle. When you're ready to dump, close the vent to the black tank and shut the dump gate on the inlet. The vacuum suction from black water leaving the tank will suck grey water into that tank.

I have no idea if it's a great idea to dump grey into black, but this seems like it would do the thing without pumps/filters.

 

[Inner Love]

I had the idea of, since the greases & fats are what amalgamate the other solids, creating a continuously rotating trommel inside of a 5 gallon bucket.

The reason for the rotation is to prevent the globs from sticking to the cylindrical screen, or at least prevent it from completely clogging the screen. This cylinder could then be easily removed and cleaned out with a sprayer at the dump site. It could potentially go months between cleanings.

To britpotato, I don’t believe there would be enough suction to completely empty the gray water tank, even without considering the loss of suction after the graywater level is below the top of the pipe.

I look forward to completing my tankage over this summer and showing everyone my implementations of what I’ve posted about since I’ve joined over 3 years ago.

 

[turf]

I look forward to completing my tankage over this summer and showing everyone my implementations of what I’ve posted about since I’ve joined over 3 years ago.

me too!!!!!

post it up!!

ok, are you planning to dispose of the water? differently than at a waste dump? what is your need to treat or clean the waste? sanitary? personal? medical? i can certainly see the need/desire for a chemo patient to dispose of waste differently. here are some suggestions to strengthen your plan.

in addition to your ptrap, hepvo, settling tank, overflow tank, sand filter, grease trommel system, you could consider:
more filtration like r/o
more sanitation like uv sterlization
self contained disposal like an evaporation pan or incinerator.

just think,
you could instal an evap pan on the roof. pump all your waste up there and let it blow away.

 

[Inner Love]

My main goal with the configuration is to have an easier time of flushing out accumulated solids, I’ve decided to not go with a dedicated solids trap as that would be just as much work as spraying out tanks on both sides. My previous post describes what I want to now build, as it accomplishes most of my original design goals and doesn’t have bespoke components to build or clean out.

I have always dreamed about evaporating greywater, and my plan for that is to use 2” vent pipe from both greywater tanks and install a 3” centrifugal 12v blower fan into the greywater overflow tank (which is really a secondary tank). The outlet of the vent pipe would be above the roof so smell would be dispersed in the turbulent air downwind of the rig.

I don’t need or want to do onboard wastewater treatment, and will not be using any drugs that would need special wastewater treatment. I plan to dump my wastewater at places where it goes to a WWTP.