Dry well

[6togo]

I'm working on getting power to my new garage and I dropped a water line in the trench while I was at it so I can have water as well. I want to install a hand wash sink in it and pipe the gray water to a dry well. What's the best way to construct a well and how large would I need? The house has a few dry wells for down spouts and the ground is very sandy so it drains well.

 

[mike93lx]

I'd make sure you aren't running afoul of any public health department restrictions on that. Could cause a problem with a sale down the road.

If it's really just hand washing, volume will be really low and with well draining soil, I bet you could do a small, 5 gal bucket chamber. Hand washing will be around 2gpm for 30-60 seconds.

 

[Renegade1LI]

Always go bigger than what you think you need. I never heard anyone say their drainage system is too big.

 

[6togo]

I'm going to gently ask the septic dept. about gray water rules in my area but I'm still going to do it regardless. I'm not putting anything down the drain besides dirty hands no chemicals or paints maybe a emergency pee! I used to do dry wells when we were building homes which were basically a large hole predetermined by the engineer filled with #57 stone lined with fabric. The pipe dropped right in the center of the stone and it was holed drain pipe. They do have the small pits also but I want it buried and would worry about someone or something falling through the top if it wasn't deep enough.

 

[NUTTSGT]

I know people would get a plastic 55 gal drum, drill the sides full of holes, fill with stone and bury that.

The drum just easily contains the stone for a future removal.

 

[6togo]

Maybe even a sump pump pit. So they fill the drum with stone? The kits they now sell have the drum empty and stone around it for the water to bleed off into as it rises in the tank through the holes in it.

 

[dcg9381]

Another option is water collection. We simply pull water off of the gutters on the shop, collect it in a tank, run it through a sediment filter / UV - and that's our water source. Lots of general aviation hangers up my way do this also. You'd be surprised how fast you can fill a tank.

Downside in cold climates is that you've got to worry about freezing, but there are options to handle that.

 

[6togo]

Water is not a issue I have that drainage is the issue.

 

[billconner]

Simply not allowed in NYS fwiw. I am thinking about a cabin for summer and quite clear I need a full septic system even with a composting or incinerating toilet. Gray or black, full engineered septic system in NYS.

 

[HoosierBuddy]

What I did in a similar situation was to run the drain line out to the yard and into a catch basin with holes drilled in the bottom with a grated top (available at Lowes, HomeDepot, etc.) This was installed in a spot in the yard where the grate would be lower than the floor in the garage. Then I hooked onto the outlet side of the catch basin with perforated drain pipe and trenched in about 12 feet of it on the outlet side of the catch basin, installing that at increasing depth so it drains away from the catch basin and backfilled all that in some large crushed stone (think I used #2).

So...what happens is the drain line drains to the catch basin. Small flows go through the bottom holes into #2 limestone and out to surrounding soil. Large flows will eventually need to flow out the perforated tile and into the crushed stone in that trench. However, if the soil is saturated such as during a heavy rain, the water will overflow through the grate and into the surrounding yard rather than backup into the garage.

 

[larry4406]

Gravel has a void ratio of around 0.4. Thus 40% of the occupied gravel volume is available for water.

Figure out your max anticipated discharge, dump that into 40% of the stone volume, and then determine your pit size.

Here are some construction pictures of a rain water drywell from the day job. It’s 2x2x2’.

The walls are lined with Geotech fabric and staples. The drain pipe inside the well is perforated. There is a 6x6” steel plate at the bottom of the observation well. It is filled with 57 gravel and covered with the same Geotech fabric. Floor of well is native soil.




In our case, we have a pop up overflow cap on the observation well. Approximately 12” of soil cover.

 

[mike93lx]

Gravel has a void ratio of around 0.4. Thus 40% of the occupied gravel volume is available for water.

Figure out your max anticipated discharge, dump that into 40% of the stone volume, and then determine your pit size.

Here are some construction pictures of a rain water drywell from the day job. It’s 2x2x2’.

The walls are lined with Geotech fabric and staples. The drain pipe inside the well is perforated. There is a 6x6” steel plate at the bottom of the observation well. It is filled with 57 gravel and covered with the same Geotech fabric. Floor of well is native soil.




In our case, we have a pop up overflow cap on the observation well. Approximately 12” of soil cover.

How do you measure the soil drainage? Dump a volume of water and time it? Doesn't it slow down once saturated?

 

[sjvicker]

Since its only a hand washing sink with very little usage I wouldn't worry about it and would just dump it to the ground. A gallon or two here or there isn't going to matter on the lawn.

I'd take it one step further and put a hose bib on the inside of your garage and connect the sink to that. When you want to move you just yank the sink out and all that's left is a hose bib.

 

[larry4406]

How do you measure the soil drainage? Dump a volume of water and time it? Doesn't it slow down once saturated?

Good question. I just follow our site plan. There are test borings typically done prior along with perc tests.

I watched one perc test in a very large drywell (20x15x3’). After excavation the soils guy took a 5 gallon bucket that had its bottom removed. He put it at the bottom of the newly excavated pit, mounded dirt around the perimeter, filled it to the top with water (5 gal), and timed how long it took to percolate/absorb into the earth. I think he repeated that test in the same spot 1 or 2 additional times; he was on site for several hours, at least half the day. I don’t know the drain times he measured or the criteria but he gave us the thumbs up to continue.

The site plan for that large drywall references a measured infiltration (perc rate) of 1.0 inch/hour and they had used 50% of that as a design value. Bunch of calcs for the amount of roof water generated for design storm, amount perked, amount stored via the void ratio, etc.

You being on septic you should have the soils report from it. It will guide you on the layers encountered as you go down.

I’m not a soils guy.

 

[mike93lx]

Good question. I just follow our site plan. There are test borings typically done prior along with perc tests.

I watched one perc test in a very large drywell (20x15x3’). After excavation the soils guy took a 5 gallon bucket that had its bottom removed. He put it at the bottom of the newly excavated pit, mounded dirt around the perimeter, filled it to the top with water (5 gal), and timed how long it took to percolate/absorb into the earth. I think he repeated that test in the same spot 1 or 2 additional times; he was on site for several hours, at least half the day. I don’t know the drain times he measured or the criteria but he gave us the thumbs up to continue.

The site plan for that large drywall references a measured infiltration (perc rate) of 1.0 inch/hour and they had used 50% of that as a design value. Bunch of calcs for the amount of roof water generated for design storm, amount perked, amount stored via the void ratio, etc.

You being on septic you should have the soils report from it. It will guide you on the layers encountered as you go down.

I’m not a soils guy.

Thanks. I don't have data on my current field but had to have the front yard tested as a reserve location when we did the pool. Result was needing a big field. The area all around my current field never gets dry, so I suspect it's from the effluent.

I hate septic.

 

[larry4406]

Thanks. I don't have data on my current field but had to have the front yard tested as a reserve location when we did the pool. Result was needing a big field. The area all around my current field never gets dry, so I suspect it's from the effluent.

I hate septic.

Go to your local health department. Since you are the owner, they should give you free of charge copies of all septic records for your parcel; at least the one here in Fauquier County VA does. These will include any County soils data as well as any reports from private on-site soils evaluators. They charge realtors and prospective buyers making copies of records for properties that the looky-loo's are chasing.

My County's GIS mapping system also has soils data on it.

Septic - rule of 3 P's; Pee, Poop, and Paper (that's it). Avoid antibacterial soaps, use liquid vs granular detergents, buy paper that is rated for septic systems. Normally they are a non-issue if soils are proper, design is proper, they are treated properly, and maintained properly. In my experience homeowner mistreatment and neglect are the main issues. Check all your toilets to make sure they are not leaking at the flapper (put dye in tank to see if bleeds to bowl) and make sure tank level is not too high and draining down the overflow.

 

[mike93lx]

Go to your local health department. Since you are the owner, they should give you free of charge copies of all septic records for your parcel; at least the one here in Fauquier County VA does. These will include any County soils data as well as any reports from private on-site soils evaluators. They charge realtors and prospective buyers making copies of records for properties that the looky-loo's are chasing.

My County's GIS mapping system also has soils data on it.

Septic - rule of 3 P's; Pee, Poop, and Paper (that's it). Avoid antibacterial soaps, use liquid vs granular detergents, buy paper that is rated for septic systems. Normally they are a non-issue if soils are proper, design is proper, they are treated properly, and maintained properly. In my experience homeowner mistreatment and neglect are the main issues. Check all your toilets to make sure they are not leaking at the flapper (put dye in tank to see if bleeds to bowl) and make sure tank level is not too high and draining down the overflow.

Appreciate the feedback. There's a bunch of back story that I won't get into here.

No toilets are running and I am super careful about what goes down the drain. I do have a stupid alternative system though...can't wait til the county gets a pipe in front of my house

 

[theoldwizard1]

I know people would get a plastic 55 gal drum, drill the sides full of holes, fill with stone and bury that.

The drum just easily contains the stone for a future removal.

If the ground is very sandy, wrap the drum with heavy grade geotextile fabric.

 

[6togo]

Think I'm going to do a simple stone pit like Larry's 10' or so from the garage with a overflow top just in case.