So you just got handed this as-built form for your septic system and… what the heck do all these numbers mean? I get it. First time I saw one, it looked like someone threw GPS coordinates, measurements, and technical jargon into a blender.
But here’s the thing - this document is basically your septic system’s birth certificate. And unlike your actual birth certificate that sits in a drawer forever, you’re gonna need this one. Selling your house? Need it. System problems? Need it. Adding that mother-in-law suite? Definitely need it. Understanding this document is critical for Idaho homeowners managing their septic systems.
Let me walk you through this form like I’m standing right there with you, pointing at each section and explaining why it matters.
The Header Section: Basic Property Information
Right at the top, you’ve got what looks like standard paperwork stuff. But every single field matters.
Permit Number: This is your system’s official ID number. Think of it like your car’s VIN. When you call the health district about anything septic-related, this is the first thing they’ll ask for. Write it somewhere else too - inside your electrical panel door is where I keep mine.
Parcel Number: This ties your septic to your specific property in county records. Mess this up and your neighbor might end up owning your septic records. Yeah, that’s a fun conversation.
Date Received: When the health district got your application. Why’s this matter? Permits expire. If there’s a huge gap between this date and installation, might indicate problems or delays you should know about.
Property Address and Legal Description: This better match your deed exactly. I’ve seen sales delayed because the address on the as-built was “123 Main” but the deed said “123 Main Street.” Bureaucracy at its finest, but it matters.
The legal description part - Township, Range, Section, Lot, Block - that’s the surveyor’s way of pinpointing your exact spot on Earth. Your installer probably got this from your deed or survey. If these numbers are wrong, your as-built might be documenting someone else’s system.
The Owner and Applicant Information
Seems straightforward, right? Not always.
If the applicant name is different from the owner name, that’s usually a contractor or previous owner. This tells you who actually pulled the permit. Sometimes that matters - like when you’re trying to track down who installed this thing 15 years ago because something’s wrong.
Pro tip: If you’re buying a house, make sure the owner name on the as-built matches the seller. I’ve seen situations where the as-built was never transferred from the builder to the first owner. Paperwork nightmare.
The As-Built Diagram (Not to Scale)
“Not to scale” doesn’t mean “wildly inaccurate” - it means don’t use this to dig. But this diagram should show:
- Where your tank sits relative to your house
- Drainfield location and orientation
- Well location (yours and neighbors within 100 feet)
- Property lines
- Any surface water (streams, ponds, ditches)
This sketch is golden when you need repairs. Your pumper can find the tank. Your contractor knows where NOT to put that new deck. The power company knows where not to drive their truck.
If your diagram is just a square with an X on it? That’s not enough detail. Good installers draw good diagrams. Lazy ones… don’t.
System Type and Materials: The Technical Meat
Now we’re getting into the stuff that actually tells you what you’ve got buried in your yard.
System Type
“Standard gravity”? That’s your basic system - wastewater flows from house to tank to drainfield by gravity alone. Simple, reliable, no power needed.
“Pressure distribution”? You’ve got a pump sending wastewater to the drainfield in controlled doses. More complex, needs electricity, but works in challenging sites.
“Alternative system”? Could be anything - sand filter, aerobic treatment, drip distribution. These need more maintenance and attention. If you’ve got one, you better understand it.
Gravel and Sand Quantities
Those yard measurements tell you how much rock and sand went into your drainfield. Why care? Because if someone says you need a new drainfield and quotes you for 50 yards of gravel but your as-built shows they only used 30 yards originally, something’s fishy.
Normal 3-bedroom system uses 30-40 yards of drain rock. If your as-built shows 10 yards? Either it’s wrong or you’ve got a non-standard system.
Tank Information
Septic/Trash Tank Gallons: This is your tank’s capacity. Standard is 1,000 gallons minimum, plus 250 gallons per bedroom. Got a 3-bedroom house with a 900-gallon tank? That’s undersized and might explain why you’re having problems.
Tank Manufacturer: Matters for warranty issues and if you ever need parts (like risers or lids). Local manufacturers are usually better - easier to get parts and service.
Depth to Tank Lid: WRITE THIS DOWN SOMEWHERE ELSE TOO. When your tank needs pumped at 10 PM on Christmas Eve (because that’s when these things fail), knowing the lid is 18 inches down saves digging up your entire yard.
Installation Measurements
Installation Depth: How deep your drainfield pipes are buried. Shallow (less than 6 inches)? Watch out for freezing. Deep (over 3 feet)? Oxygen might not reach the bacteria that treat waste.
Rock Under Pipe: Should be at least 6 inches, typically 12 inches. This is where the treatment happens. Less rock = less treatment = potential problems.
Standpipe/Riser Information
If these fields are filled in, you’ve got access ports to surface level. That’s fantastic - means you don’t have to dig to inspect or pump. If these fields are blank, consider adding risers. Best $500 you’ll spend.
The GPS Coordinates (Latitude/Longitude)
Newer as-builts include GPS coordinates, and this is brilliant. Why? Because finding a buried tank or drainfield 20 years later is like finding buried treasure without a map.
Those coordinates should be in decimal degrees (like 43.6150° N, 116.2023° W) or degrees/minutes/seconds. Either way, you can punch them into Google Maps and find your system components within a few feet.
If your installer took these coordinates, they’re forward-thinking. If not, consider getting them yourself with a phone GPS app next time the tank is exposed.
Drainfield Specifications: The Critical Numbers
This section tells you everything about your drainfield’s capacity and design.
Drainfield Dimensions
Width and Length: Multiply these for total area, but remember - effective area might be less. A 20’ x 100’ drainfield is 2,000 square feet, but…
Installed vs. Effective Square Footage: Installed is what got built. Effective is what counts for capacity. The difference? Effective area excludes things like non-perforated pipe sections and turn-arounds. If effective area is way less than installed, ask why.
The Math That Matters
Standard sizing: 2-bedroom = 600 sq ft minimum, 3-bedroom = 800 sq ft, 4-bedroom = 1,000 sq ft. But soil type changes everything. Clay soil might need double these numbers.
If your as-built shows 600 sq ft for a 4-bedroom house? Either there’s an error or you’ve got exceptionally good soil. Or someone screwed up. Probably that last one.
System Components: The Checkboxes
Those little yes/no boxes tell you what extra components you have:
Distribution Box (D-Box)
“Yes” means you’ve got a concrete or plastic box that splits flow evenly between drainfield lines. These can settle and cause uneven distribution. If you’ve got one, it needs checking every few years.
Drop Box
Used on slopes to control flow between serial distribution trenches. If you’ve got one, you’ve got a sloped lot. These need more frequent inspection because they can clog or tilt.
Valve
Usually means you can alternate between two drainfield areas. That’s actually awesome - lets one side rest while using the other. If you’ve got this, learn how to use it.
Distance Measurements: The Safety Zones
Those distance measurements to tank and drainfield from well? They’re not suggestions.
Well to Tank: Minimum 50 feet Well to Drainfield: Minimum 100 feet Property Lines: Usually 10 feet minimum Foundation: 10-20 feet depending on type
If any distances are less than required, there should be an explanation in the notes. “Existing well, variance granted” is legit. Blank notes with short distances? That’s a problem.
Technical Allowance Section
If this box is checked “Yes,” something about your system doesn’t meet standard requirements but was allowed anyway. This isn’t necessarily bad - maybe you’ve got great soil allowing reduced sizing, or maybe existing site conditions required creativity.
But you need to know what that allowance was for. Check the notes section. If it’s not explained, call the health district and ask. Technical allowances can affect future repairs or modifications.
The Notes Section: Where the Real Story Lives
This is where inspectors and installers put crucial information that doesn’t fit in boxes:
Good notes might say:
- “Existing well at 85 feet from drainfield, variance approved per letter dated…”
- “Additional 200 sq ft reserve area located north of existing drainfield”
- “Pump alarm installed in master bedroom closet”
- “System designed for future 2-bedroom addition”
Bad notes are either blank or say unhelpful things like “installed per plan.” What plan? Where is it?
If your notes section is blank but your system has anything unusual about it, that’s a documentation failure that’ll bite you later.
Common Red Flags in As-Builts
After reading hundreds of these, here are the warning signs:
Missing Information
Blank fields everywhere? Either lazy documentation or the installer was hiding something. Every field should have something, even if it’s “N/A.”
Mismatched Numbers
Tank size doesn’t match bedroom count? Drainfield size seems tiny? Depths don’t make sense? These need investigation before they become problems.
Need Help Decoding Your As-Built? Our inspection team can review your as-built documentation, verify accuracy, and explain what it means for your system’s future. Schedule an inspection →
No Installer Signature
If the installer didn’t sign, why not? Did they not want liability? Was there a dispute? Unsigned as-builts are problematic for resale and repairs.
Vague Diagram
A rectangle with an X doesn’t cut it. You need enough detail that someone could find components without destroying your yard searching.
How Inspectors Read These Forms
When an inspector looks at your as-built, they’re checking:
- Compliance: Do all measurements meet code?
- Completeness: Is everything filled out?
- Consistency: Do the numbers make sense together?
- Clarity: Could someone else understand this?
They’re also comparing it to the original permit application. Major differences need explanation. If the permit was for 1,000 sq ft but the as-built shows 600 sq ft, that’s a conversation.
What to Do With Your As-Built
Make Copies
Physical and digital. Store them in different places. Email yourself a PDF. This document is irreplaceable if lost.
Verify Accuracy
While everything’s still visible (before backfill), check the measurements yourself. Depth to tank lid? Measure it. Distances? Pace them off. Trust but verify.
Add Your Own Notes
Create a supplement with:
- Photos during installation
- Extra measurements (like tank lid GPS coordinates)
- Pump model and manual (if applicable)
- Installer contact information
- Any warranty information
Update When Changes Occur
Added risers? Note it. Replaced pump? Document it. Extended drainfield? Get a new as-built. Your future self (or buyer) will thank you.
Using Your As-Built for Maintenance
This document guides all future work (and our complete service list covers all these needs):
For Pumping: Tells pumpers where to find access, how deep to probe, tank capacity for complete pumping. Learn more about pumping services →
For Repairs: Shows what you have, where it is, how it was built. Saves diagnostic time and digging.
For Additions: Proves your system capacity, shows reserve areas, documents what’s already used.
For Troubleshooting: Helps identify whether problems are likely tank-related (near house) or drainfield-related (in yard).
When As-Builts Go Wrong
Sometimes the as-built doesn’t match reality. I’ve seen:
- Tank in completely different location
- Drainfield 50% smaller than documented
- Wrong type of system entirely
If you discover discrepancies:
- Document what you actually find (photos, measurements)
- Contact the original installer if possible
- Work with health district to correct records
- Get an amended as-built issued
Don’t just live with wrong documentation. It’ll cause problems forever.
The Digital Evolution
Newer health districts are going digital with as-builts. Benefits:
- Can’t lose them
- Easy to share with contractors
- GPS coordinates automatically plotted
- Photos can be attached
- Updates tracked with version history
If your district offers digital as-builts, use them. If not, create your own digital version.
Special Situations and What They Mean
Multiple As-Builts
Got more than one? Usually means repairs or expansions. You need all of them to understand your complete system.
Partial As-Builts
Sometimes only tank replacement or drainfield repair gets documented. These supplement but don’t replace your original as-built.
Historic Systems
Pre-1970s systems might have no as-built at all. If you’re creating one retroactively, note “as-found condition” and date of documentation.
The Bottom Line on As-Builts
This document is your system’s permanent record. It’s the first thing anyone needs to work on your system, the key document for selling your property, and your reference for all maintenance.
A good as-built is:
- Complete (every field filled)
- Accurate (measurements verified)
- Clear (anyone can understand it)
- Preserved (multiple copies, multiple locations)
A bad as-built causes problems forever. If yours is lacking, work on improving documentation now while you can still verify information.
Your as-built isn’t just paperwork - it’s the instruction manual for a $15,000+ system that needs to last decades. Treat it with respect, keep it safe, and understand what it’s telling you.
That jumble of numbers and technical terms? Now you know it’s actually the story of your septic system - where it lives, how it was built, and what it needs to keep working. And unlike most stories, this one better have a boring middle and a happy ending.
Keep that as-built safe. Future you is counting on it.
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