Drywells for pool & water softener backflush and yard drainage

Drywell leach pit kits can dispose of pool filter and water softener backflush, French drain, storm water, yard drainage, driveway runoff, roof gutter, or basement sump pump effluent. Dry building foundations save an enormous amount of heating and cooling energy. Nothing worse for your septic system than water softener backflush salts and pool chemicals. Drywells can also be used for septic system leach pits and are a great solution for repairing failing septic system leach fields. One of our favorite, most practical products and made right here in the U.S.A. from 100% recycled plastic. These 2 foot diameter by 2 foot tall (plus 5 inch high lid) 28.75 inch overall height, heavy-duty, high-density polyethylene HDPE drywells come shipped in a handy twenty-six pound carrying case (26" x 10" x 25" box) ready for on-site assembly. Each drywell provides 48+ gallons of initial surge capacity, which is equal to 74 lineal feet of four inch diameter sewer pipe, but ultimate capacity of your leach pit is unlimited. With several feet of gravel under and around it, a single drywell could dispose thousands of gallons of water in properly percolating soils. Additional drywells provide more initial surge capacity before the water disperses into surrounding gravel, which is handy in poorly percolating clay and bedrock soils. At least one drywell per gutter is best practice for roof runoff. Gutter downspouts that allow rainwater to soak the soil around your house do nothing but steal energy in the summer and winter alike. The key to a dry, waterproof basement is taking roof gutter runoff at least 20 feet away from the foundation. Drywell system cut sheet with gravel installation details is posted for engineers.

Sample installation shown below with TWO DRYWELLS in series and bringing effluent in through the lid. Top loading (with vent grate as included in kit) ensures maximum surge capacity. Note that venting your leaching pit or any septic field is most highly recommended... lack of venting at both ends of lateral lines is the ultimate cause of leach field failure (after lack of proper two compartment filtered septic tank). Oxygen keeps the drainage pit dry and the soil around it healthier. Freezing is rarely, if ever, a problem with running sewage water underground, but you can always cap the vents in deep winter, if need be. We provide all of the fittings pictured with your kit (4 inch sanitary tee, riser, coupler, and green vent grate). Plus, a 6by6 foot piece of geotextile fabric for above the gravel layer to keep backfill soil from clogging the surrounding leach pit rock. Additional fabric can be purchased below for leach pit sides. Fabric on the sides is recommended in sandy or silty soils or areas of high seasonal groundwater. Drywell system cut sheet with gravel installation details is posted for engineers.

Drywell kit comes with three interlocking side panels, cover lid, sanitary tee fitting, coupler, riser pipe section, green slotted surface vent grate, and 6 foot by 6 foot piece of heavy-duty woven geotextile filter fabric to keep soil from entering the gravel layer from atop your drywell. Additional fabric can be purchased below for the sides of your leach pit. Fabric on the sides is recommended in sandy or silty soils or areas of high seasonal groundwater. Never place geofabric on the bottom side of a septic system leach pit, only the sides and top of gravel.

Knock out all of the one inch ports in drywell side panels to allow water to drain freely. Hit the "X" marks on the inside of each panel squarely with a small head hammer while resting the outside of the drywell atop a 2 by 4 board laid close to the hole being removed. Support alongside where you pound the hammer will prevent cracking.

Place two panels side by side and align the male tabs with female flanges on adjoining panel. Slide male tabs downward until the panel edges are level at the top. Repeat steps for the third panel. Set lid cover atop the assembled side panels and rotate until flanges are aligned with cover screw locations. You can insert three 2 inch deck screws through lid into side panels to increase stability while backfilling, but that makes it difficult to remove lid for cleaning or inspecting later.

Knock out the hole in lid center and insert the sanitary tee fitting. It is not necessary to glue this fitting in place. One can send a deck screw or two in from the sides to stabilize while backfilling, but that only makes it difficult to remove for cleaning or future relocation. Then insert the section of four inch pipe riser, coupler and green vent grate supplied with kit.

Venting your leaching pit is VERY important for good soil health and long-term percolation performance. The vent grate (included with kit) allows inspection, cleaning and most importantly AIR into your leach pit. Oxygen keeps your pit dry between soakings and the soil around it much healthier. Stagnant soil goes septic, creating a dense bio-mat that prevents water from percolating into the ground. Freezing is rarely, if ever, a problem with running water that far underground, but you can always cap the vents in deep winter, if need be.

When leaching roof gutter water, always vent the downspout to insure against backup and 'burping'. In practice, this amounts to not sealing around where the rectangular gutter enters the four inch drain pipe. They make a special pipe fitting for the transition from gutter to pipe, but just leaving it open will allow air into the gap around downspout.

Best practice is to bring a 4 inch diameter SDR35 'sewer' pipe from foundation to the drywell or settling basin. Schedule 40 thick-wall pipe is not necessary and a diameter smaller than four inch can fill and 'burp', since it is not under pressure, and freeze in a cold climate. We recommend starting with a rubber boot coupler at the foundation to transition from household effluent pipe to the 4 inch run to drywell. This will allow pipe to settle a bit without compromising that joint.

We recommend installing drywell leach pits at least ten feet away from home foundation, if not twenty feet or more. Local building code may allow closer installation, but keeping your foundation dry ensures best energy conservation and integrity of concrete footers. Vehicular traffic atop drywell should be avoided. They are not warranted by manufacturer.

Key with any drywell installation is to loosen 'scarify' the soil up to a foot below the base of the leach pit. This is particularly important when digging by hand, as you do not wish to leave compacted soil in the bottom of the pit. Soil needs to be loose to percolate properly. Also scarifying the soil on side of leach pit is recommended in clay and hard-pack conditions.

Water freezing in a leach pit is never a problem when enough gravel is placed under and around the drywell. In poor percolating soils, one just digs a larger and deeper leach pit and installs more gravel to allow room for percolation. One foot of gravel under and around a drywell and then up to the lid, should be considered a bare minimum. Two feet of gravel under and around the sides of a drywell is the most common specification for longevity and capacity.

Septic and greywater systems should use crushed washed aggregate, not round river rock. Minimum 'nominal' 3/4 inch is typical and often referred to as a #57 crushed. Up to 1-1/2 inch aggregate can be used, but it gets harder to shovel and may not be quite as effective for septic system effluent treatment. Avoid 'pea gravel', chips and fines, dirt and sand. Avoid using larger gravel or round river rock. Gravel smaller than 3/4 inch will fall through the one inch knock-out holes in side of drywell. Never put gravel on the inside of the drywell, only around the exterior.

Place assembled drywell atop the gravel in base of leach pit and level. Add gravel in stages around the drywell up to level of lid and then cover the top of gravel with the enclosed geotextile fabric. Shiny side of fabric facing towards the drywell. We supply enough material to cover the top of a six foot by six foot hole. In sandy and silty soils, you can purchase additional geotextile fabric from us to line the sides of the leach pit. It is important to keep soil from migrating into the gravel layer.

Backfill atop the geotextile fabric with at least eight inches of native soil leaving the site mounded to direct surface water away from the leach pit area. The more soil coverage above drywell, the easier it is to regrow a yard. In poorly percolating soils, you can bring the gravel around drywell all the way up to finish grade to allow evaporation in addition to percolation. If you are not planning to fill under and around with gravel (not recommended), wrap geotextile fabric around the drywell sides to prevent soil from entering drain holes and secure in place with tape duct.

IMPORTANT NOTICE: It is your obligation to determine whether this product is suitable for the intended use and particular application. Consult your building officials to insure compliance with all building codes and requirements. These step-by-step instructions provided reflect mechanical assembly only. Additional information may be necessary to insure proper results for all applications. Consult with professionals to determine special soil conditions and structural requirements. Drywell system cut sheet with gravel installation detail is available for engineers.

Residential home sewage system (septic) leach fields, roof gutter runoff, driveway and yard drainage are common applications for drywells. It is not necessary to have multiple drywells to dispose of additional water, just a larger hole (leach pit) filled with more gravel. It is a nice engineering touch though, to install at least two drywells in series, per the image above. This arrangement allows the first drywell to act as a settling basin for dirt, leaves, and other particulates, ensuring a long lasting system by keeping the second drywell free of debris. Units can be stacked to increase the amount of surge potential for storm or sewage water disposal. The "capacity" of a drywell system is only limited by the size of the gravel filled hole you put it in (leaching pit). The drywell itself is about fifty gallons dry (surge potential), but this quickly disperses into the surrounding leach pit filled with 3/4 to 1-1/2 inch crushed aggregate. You cannot have too large of a leaching pit when disposing of large amounts of water - extra large leaching pits ensure the longevity of your soil percolation.

Your local building department sets the equations (code) used to determine minimum leach pit size for septic systems and yard drainage. Knowing the actual percolation rate of the soil is the only way of being certain, so you need to hire a local soil engineer to be positive leach pit sizing. A rule of thumb in well percolating soil is up to about 200 gallons per day, every day, with at least 1 foot of gravel under and around the drywell. With gutter and downspout rain water disposal, a two (2) inch rainfall is 1.25 gallons per square foot of roof (1 gallon is 231 cubic inches) 1 cubic foot is 1728 cubic inches or 7.48 gallons. A 1000 square foot roof, generating about 1250 gallons of water in a two inch rainfall, would, as a very general rule of thumb, require a gravel filled hole (leaching pit) large enough to hold that amount of water when empty. Based on volume alone, not actual percolation rate of the soil, a 4' by 4' by 12' long leach pit can be estimated to disperse about 1250 gallons of rainwater in most soils. A hole this size could use at least two drywells (100 gallons of surge) or more in slower percolating soils, where you may wish to stack them. Drywell system cut sheet with gravel installation detail is available for engineers.

Water softener backwash brine and washing machine water should not be run through your septic tank. Septic tanks function by "digesting" solids while detergents, salt and other anti-microbial chemicals slow/stop this natural bacterial digestion. Always run water softener brine backwash to a separate drywell disposal area (leach pit). Ideally, all greywater (showers and sinks) would also be diverted to separate leach pits, but at least divert your soapy washing machine water (greywater). Most manufacturers can provide a removable center spindle lint filter for your washing machine. Anyone on a septic system should ALWAYS trap lint before being sent to septic tank. Only folks on city sewer can just send it down the drain. And like any project... there are Good, Better and Best approaches with greywater disposal in drywells. Good... with cleanable/removable lint filter on your washing machine (does not backflush lint down the drain) you could install at least one drywell kit. Better... 2 drywell kits in series allows the first drywell to act as lint & sediment trap. Best... greywater systems subject to laundry lint, sediment and/or grease from sinks should invest in a full Greywater System with settling tank and filter.

Drywell kits are also excellent for use with greywater reuse systems. Sometimes you must divert greywater away from your orchard or planterbed for simple disposal. See director valve fitting for details on how to split flow 50/50 or all one direction. Fruit trees, for instance, benefit from having their root systems go dry for a few days. As with all of our products, we'll work closely with you, providing toll-free consultation during construction! Please note that you should ALWAYS install a settling tank filter basin in-line before your leach field or run the risk of clogging it with grease and fats and filling with solids like hair and laundry lint. You can simply install a drywell, or two, for your washing machine and have direct input. Just keep in mind that all of that lint and grease is going to slowly build up, eventually clogging the first drywell the unfiltered greywater spills into. That is why you have to install at least two drywells in series when not installing a filter basin settling tank.

Three or more drywells can be installed in-series, bringing storm water into the first drywell to act as a sediment catch for leaves, salt, grease, lint, or other run-off erosion soil debris. Venting your leaching pit is VERY important for good soil health and long-term percolation performance. The vent grate (included with kit) allows inspection, cleaning and most important of all, AIR into your leach pit. Oxygen keeps your pit dry between soakings and the soil around it much healthier. Stagnant soil goes "septic", creating a dense bio-mat that prevents water from percolating (absorbing) into the ground. Top loading (sending water into drywell through lid with enclosed kit venting parts) also ensures maximum surge capacity for the drywell. Freezing is rarely, if ever, a problem with running water, especially far underground, but you can cap the vents in deep winter, if need be.

Sewage disposal septic systems are commonly designed as gravel-filled leach pits with drywell(s) on smaller properties. Leach pits disturb much less surface area than a leach field of perforated four inch diameter sewer pipe in a shallow gravel bed. Seasonal groundwater must not be a local issue when designing deeper leach pits. Figuring at least a foot of soil cover atop lid for a yard and at least a foot of gravel underneath for optimal percolation. Please note two critical design errors in the second sketch... 1) Never install bends in the four inch diameter sewer pipe before the septic tank. Bends after the tank are fine since the water has been filtered of solids, but you don't want to clog the line coming into the tank. 2) always install a cleanout in the sewer pipe immediately after it leaves the home foundation. Should that line clog or freeze, you need a means to access it. Maintain 1/8 to 1/4 inch per foot drop from house to inlet side of septic tank. Any steeper, and water might flow too fast and pass right around toilet waste. From the outlet side of septic tank, effluent can flow downhill at a much steeper angle. Always 'bed' all pipe and tank well, in plenty of gravel. A 6-8 inch layer or 3/4 to 1 inch diameter aggregate is recommended. Gravel ensures accurate pipe slope in trenches since this size crushed rock only compacts about 3% to 5% later. Bedding pipe prevents dips and flat spots where sewage might collect. In a cold climate, it is critical to avoid allowing sodden soil (frost) from touching your pipe and tank. Even in a warm climate, septic tanks are able to maintain healthy bacteria levels and 'digest' sewage more readily when warm. Bedding a septic tank in gravel can make all the difference between having your tank pumped every three years to maybe once every five or six years.

Drywell leach pit kits are best practice for additions and repairs on pipe-in-gravel leach fields. Not venting the end of each leach field lateral line (finger) is the most common cause of leach field failure. Lack of fresh air in the leach field pipes and surrounding gravel creates anaerobic conditions, accelerating bio-mat formation. Best practice is to install at least one drywell at the end of each lateral line finger. An upgrade for longevity is two drywells installed in-series which allows the first to act as a settling catchment, ensuring long-term viability of a failing sewage disposal system by keeping the perforated pipes lines dry most of the time. Drywell system cut sheet with gravel installation detail is available for engineers.

There is no 'Miracle Enzyme Cure' or hole punching scheme that will work for any length of time. Please don't believe those ads for "all natural, biodegradable, septic safe" leach field cleaners. May buy you a couple of months, but at the risk of contaminating your groundwater. Septic waste 'digesters' are not sold here. And schemes to punch holes in your yard to cure the problem are just hustles. You have to flush the biomat out of leach field pipes before any treatment.

Hire a professional to flush out leach field lines FIRST (power jetting) prior to treatment. The first time, it requires an industrial strength pressure washer equipped with rotating root cutting blades to clear the entire four inch leach field drain pipe. There is a lot of work to do before the line jetter shows up. Septic system flushing involves hazardous human waste. Wear disposable protective clothes with full head/mouth covering, face shield and/or goggles, protected sleeves and gloves. There must be a cleanout at the start of each lateral line and another at the end. A large pit at least 2by2by3 feet deep is excavated at the end of each leach field pipe to accept the flushed out bio-mat and roots. You accomplish nothing by jetting and allowing the bio-mat to remain inside of the lateral line perforated pipes.

Peroxide treatment is best left to professionals. Hydrogen peroxide is caustic and will BURN exposed eyes and skin. Home healthcare hydrogen peroxide is around 3% with pool chemical supply stores selling barrels of 30% strength up to 50%. HazMat Placards must be posted in your front and rear window. We do not sell hydrogen peroxide.

After jetting and flushing, cap both ends and CAREFULLY pour in the industrial strength hydrogen peroxide. The expense of trying to completely fill perforated pipe with hydrogen peroxide is likely not cost-effective, but invest in enough to fill the pipe at least 1/4 to 1/3 full. Per 100 lineal feet of 4 inch diameter pipe, it takes 16 gallons to fill almost 1/4 full and 20 gallons to fill 1/3 full. Plumb cleanout with a tee fitting and gasketed garden hose adapter (3/4 inch MNPT to 3/4 MGHT). Give peroxide at least a few hours to start working on the bio-mat and then pressurize the line with water for best effect. Allow line to drain and then jet and flush again to attempt to get more bio-mat out of your lines. Lacking power jetting head for four inch pipe, you can do a passable job with a high pressure sprayer equipped with disruptor head (full circle shower spray).

You have to examine why the system failed in the first place. The most common reasons are: single compartment septic tank, no septic particulate filter, under-sized leach field, and lack of leach field ventilation. Oxygen is very important for leach field health. A drywell with surface vent at the end of lateral lines is an instant fix. Greatly increases capacity and dries out the lateral lines. Taking the load off your failing leach field is crucial to any repair.

One drywell kit provides an initial surge capacity of 48+ gallons before it starts percolating into surrounding soil. That is the same effective surge capacity as 74 lineal feet of four inch diameter sewer pipe. Gravel backfill around and under the drywells will increase the capacity of your leaching pit and extend the serviceable life expectancy. A single drywell with at least one foot of gravel under and around it (absolute bare minimum) will dispose of 200+ gallons per day in most soils, but you cannot have too large of a leaching pit. The more gravel under and around the drywell, the better for longevity.

Shown above is a standard installation with two drywells in series, bringing sewage in through the lid. Top loading through the vent tee ensures maximum surge capacity. Freezing is rarely, if ever, a problem with running sewage water underground, but you can always cap the vent in deep winter, if need be. We provide all of the fittings pictured with your kit (4 inch sanitary tee, riser, coupler, and green vent grate). Plus, kit has a 6by6 foot piece of geotextile fabric for above the gravel layer to keep backfill soil from clogging the surrounding leach pit rock. Additional fabric can be purchased below for the sides of your leach pit. Fabric on the sides is recommended in sandy or silty soils or areas of high seasonal groundwater. Never place geofabric on the bottom side of a septic leach pit, only the sides and top of gravel.

Never install plastic 'visqueen' sheeting or cheap non-woven 'weed barrier' landscaping fabric in place of professional grade heavy-duty woven geotextile fabric for septic system leach fields, drywell pits, French drains, or soil stabilization in foundation drainage projects. Besides longevity, the problem with using visquene plastic sheeting or cheap weed barrier non-woven materials, is they suffocate the soil, ultimately causing anaerobic soil conditions, biomat formation, root rot, and molding issues. Plastic sheeting becomes brittle and tears within a few years and the adhesive bond holding non-woven weed-barrier fabric threads together eventually decomposes, slipping, ripping and tearing, and allowing sand and soil to migrate into the gravel drainage layer of leach field or French drain. Invest in our professional grade woven geotextile fabric with a full 35 mil thickness and extra heavy-duty five ounce per square yard weight and 12 gallons per square foot per minute water permeability. This polypropylene fabric will never rot and will effectively work indefinitely when not exposed to sunlight. Longevity and durability is a function of heavy-duty weight and tough woven construction, versus non-woven weed barrier fabrics which tend to fall apart over the years.

Geotextile fabric pricing, installation details, and design tips