Building your own septic tank is not a weekend project, but for rural homeowners, farmers, and off-grid properties, it can be a practical solution. One common DIY approach is learning how to build a septic tank with concrete blocks. Concrete block tanks are strong, customizable, and relatively affordable if you already have masonry skills. However, they must be constructed carefully to prevent leaks, groundwater contamination, or structural collapse. In this guide, we’ll walk through the basics of planning, building, and maintaining a concrete block septic tank, along with recommended tools and components ($300+) that make the job easier and safer.
Quick Picks: Essential Tools & Materials
- Bosch Professional Rotary Laser Kit – Best Overall: ensures proper leveling and slope for tank construction.
- Kraft Tool Company Masonry Block Trowel Set – Best Budget: reliable tools for laying concrete blocks correctly.
- Polylok 24″ Septic Tank Riser Kit with Lid – Best Premium: brings access to grade for safe pumping and inspections.
Buyer’s Guide: Key Factors When Building a Block Septic Tank
- Size and Capacity: A standard home septic tank is 1,000–1,500 gallons. Plan for at least this size for long-term use.
- Soil and Drainage: Your tank location must allow proper drainage to the leach field.
- Wall Strength: Reinforce concrete block walls with rebar and mortar to prevent collapse.
- Waterproofing: Seal joints with waterproof mortar or concrete slurry to avoid leaks.
- Access: Add risers and lids for easy pumping and future maintenance.
- Local Regulations: Many counties require permits and inspections—check before you build.
Step-by-Step: How to Build a Concrete Block Septic Tank
- Excavation: Dig a hole large enough for the tank dimensions, allowing space for walls and base.
- Foundation Slab: Pour a reinforced concrete base (4–6 inches thick) to serve as the tank floor.
- Block Wall Construction: Lay concrete blocks in mortar, staggering joints, and reinforcing with vertical rebar.
- Waterproofing: Apply cement slurry, hydraulic sealant, or waterproof mortar to all joints.
- Inlet & Outlet: Leave openings for inlet and outlet pipes (typically 4-inch PVC).
- Partition Wall: Add a baffle or divider wall inside to separate solids from effluent.
- Cover & Risers: Place reinforced concrete slabs or precast lids on top. Install risers for access.
- Backfill: Carefully backfill around the tank with gravel or soil, ensuring no pressure cracks the walls.
Detailed Product Reviews
Bosch Professional Rotary Laser Kit
Who it’s for: Builders who need precise leveling for excavation and tank construction.
- Key Benefits: Perfect slopes for inlet/outlet pipes; ensures tank sits evenly.
- Pros: Extremely accurate; rugged; professional-grade.
- Cons: Higher upfront cost.
Verdict: An essential tool for preventing drainage problems in DIY septic builds.
Kraft Tool Masonry Block Trowel Set
Who it’s for: DIY builders laying blocks for a septic tank structure.
- Key Benefits: High-quality trowels ensure proper mortar application and smooth joints.
- Pros: Affordable; sturdy; easy to use.
- Cons: Requires masonry skill for best results.
Verdict: A budget-friendly choice for anyone building with blocks.
Polylok 24″ Septic Tank Riser Kit
Who it’s for: Homeowners who want future access to their septic system without digging.
- Key Benefits: Brings tank access to ground level; strong lid prevents odors and accidents.
- Pros: Durable; simplifies pumping; code-compliant.
- Cons: Must match riser ring size to tank lid.
Verdict: A premium upgrade that makes long-term maintenance far easier.
Comparison Table
| Product | Type | Best For | Price Link |
|---|---|---|---|
| Bosch Rotary Laser Kit | Leveling Tool | Proper slope and layout | See Price |
| Kraft Masonry Trowel Set | Masonry Tools | Laying block walls | See Price |
| Polylok 24″ Riser Kit | Tank Riser | Easy access to tank | See Price |
FAQ
1. Is it legal to build a septic tank with concrete blocks?
In some rural areas it’s allowed, but many counties require precast or engineered tanks. Always check local regulations first.
2. How long does a block septic tank last?
If built and sealed properly, decades. Poor waterproofing can shorten the lifespan dramatically.
3. What’s the biggest risk with block septic tanks?
Leaks into soil and groundwater contamination if the walls aren’t sealed correctly.
4. Do I need rebar reinforcement?
Yes. Without rebar, walls may crack or collapse under soil pressure.
5. Can I pump a block septic tank the same way as a precast one?
Yes, as long as you’ve added proper risers and lids for access.
Conclusion
Building a septic tank with concrete blocks can be done with the right tools, skills, and waterproofing methods. While not as common as precast tanks, block systems offer flexibility for DIYers who want a cost-effective solution. Just remember: check your local codes, reinforce the structure, and seal all joints. For easier maintenance, invest in a riser kit like the Polylok 24″, and use professional-grade tools to ensure a safe, long-lasting build. Done right, your homemade tank will serve your property reliably for years to come.