Septic Tanks and the Miami Water Table
More septic than people assume
Miami-Dade County has said roughly 120,000 septic systems are still in use in the county, many of them in established neighbourhoods rather than out at the edges. Coral Gables puts sewer service at about half its population. Parts of the City of Miami, including streets in Little River, have only recently been moved to sewer. If you are not sure which you have, look at your water bill: a sewer charge means you are connected.
Why groundwater matters
A septic system works by letting liquid from the tank soak through a drainfield into unsaturated soil, which filters it before it reaches groundwater. In Miami-Dade that groundwater is the Biscayne Aquifer, close to the surface and rising with sea level. The county has estimated that about 9,000 systems are already vulnerable to failure under current groundwater conditions, and that the figure will grow to around 13,500 by 2040. In the wet season, or after a tropical storm, a drainfield sitting in saturated ground stops accepting water, and the first sign is slow drains or a backup in the lowest fixture.
Plumber, septic company, or both
Probably a plumber
One fixture slow, others fine: that is a clog in the house. A main line backing up in dry weather with a recently pumped tank: the line between the house and the tank may be blocked, broken or full of roots.
Probably a septic company
Everything slow at once, a wet or smelly patch over the drainfield, and no pumping in years. The tank may be full or the drainfield failing. Septic pumping and drainfield work are a separate licensed trade in Florida.
Possibly both
Backups that come and go with the rain. The tank may be fine and the field saturated, or the line may be cracked and taking in groundwater. A camera in the line and an inspection of the tank settle it.
Connect 2 Protect
The county's Connect 2 Protect program is extending sewer lines to areas on septic, starting with places where systems are failing or vulnerable. Its first phase included nearly 300 homes in Little River, funded by a state grant, with work scheduled to begin in 2023. Where a sewer line becomes available, county rules require properties to connect, and the county can issue a notice of required connection. Connecting means a new lateral from the house to the street and abandoning the old tank, which is plumbing work with its own permit.
Received a notice to connect, or backups every time it rains? Call to have the line scoped and the connection priced.
Where to go next
- Plumbing in Coral Gables, where half the city is on septic
- Drain cleaning and camera inspections
- Hurricane plumbing prep
Common questions
Does a plumber pump septic tanks?
Generally not. Pumping and drainfield work are done by septic contractors. A plumber handles the pipes in the house and the line to the tank, and the new lateral when you connect to sewer.
Who pays to connect when the sewer comes to my street?
It depends on the project. Some phases have been grant-funded at no cost to owners; elsewhere the owner pays for the private lateral. Check the notice and the county’s Connect 2 Protect pages for your area.
Can I add a bathroom to a house on septic?
Possibly, but a new bathroom adds load to a system that may already be under pressure from groundwater, and the permit review will look at it. Ask before you design around it.