Jobsite trailer with a restroom
Holding tank. Nobody builds a drainfield for a two-year project. The tank gets pumped on a schedule and leaves with the trailer. See office trailers.
AnswerHolding tank, scheduled pump-out
A septic system treats wastewater and lets the liquid soak into the ground through a drainfield. A holding tank treats nothing. It stores every gallon until a truck pumps it out. Septic is a permanent system built for a building with the right soil. A holding tank is what you use where there's no sewer and no drainfield: a jobsite trailer, a sales office, a remote site, or a building whose septic system is down.
Side by side
The tank in the ground can look the same. The difference is whether anything leaves it except by truck.
| Question | Septic system | Holding tank |
|---|---|---|
| Where the liquid goes | Out of the tank into a drainfield, where the soil treats it.1 | Nowhere. It stays in the tank until it's pumped. |
| How often it's pumped | EPA says household tanks are typically pumped every 3 to 5 years.2 | Every time it fills, on a schedule measured in days or weeks. |
| What it needs from the site | Suitable soil and room for a drainfield. | A watertight tank and a truck that can reach it in any weather.3 |
| How long it's there | Built to serve a building for years. | Often temporary: a trailer, a construction phase, a repair. |
| Where the cost sits | Up front, in design, permits and installation. | In the pump-out visits, every week or month it's in use. |
Septic and holding tank rules are set by states and counties. Check your local rules before you plan around either one.
Sizing
A holding tank's size sets how often the truck comes. Minnesota's rule is a useful reference because it spells it out. A dwelling needs at least 1,000 gallons, or 400 gallons per bedroom if that's more. Other establishments need at least five times their design flow, which means at least five days of storage.3
The same rule requires an alarm at 75 percent of capacity, unless the tank is pumped on a regular schedule.3 On a jobsite we'd rather have both. A schedule keeps it from filling and the alarm covers the week the crew doubles.
A septic tank works on a different clock. EPA says to pump when the scum layer is within 6 inches of the outlet, the sludge is within 12 inches of it, or the sludge and scum together take up more than 25 percent of the liquid depth.2
Call us with the address and what the tank has to serve. We'll size the holding tank, set the pump-out schedule with the local provider, and quote both together.
Which one you need
Most people asking this question aren't choosing between two permanent systems. They have a building or a site and need to know what to do this month.
Holding tank. Nobody builds a drainfield for a two-year project. The tank gets pumped on a schedule and leaves with the trailer. See office trailers.
AnswerHolding tank, scheduled pump-out
A temporary holding tank keeps the building open while the system is repaired, if your local health department allows it. Ask them first.
AnswerHolding tank until the repair is done
Where a drainfield won't work, some states permit a holding tank, with conditions like the Minnesota rule above. Expect pump-out visits to be the biggest running cost.
AnswerHolding tank, if permitted
Keep the septic systems and put the pumping on a schedule. Across many sites, the hard part is knowing which tank is due.
AnswerScheduled septic pumping
Before you call
Five answers get you a tank size and a pump-out schedule on the first call.
A trailer restroom, a building, a sink, a shower. Fixtures set the daily flow.
Today and at the peak. Tanks get sized for the peak.
Where the water comes from, and whether there's power for a high-level alarm.
Where a pump truck can park, in mud and snow as well as dry weather.
A few weeks, a construction phase, or open-ended. It changes what we'd recommend.
Common questions
No. A septic tank settles solids and sends the liquid out to a drainfield, where the soil treats it. A holding tank has no outlet. Everything stays in the tank until a truck pumps it out.
Every time it fills, which depends on its size and how much flows in. Minnesota requires tanks for non-dwelling uses to hold at least five days of design flow, and an alarm at 75 percent unless pumping is regularly scheduled. We set the schedule from the daily flow.
EPA says household septic tanks are typically pumped every 3 to 5 years and inspected at least every 3 years. Systems with float switches, pumps or mechanical parts should be inspected more often, generally once a year.
Temporarily, often yes. Permanently, it depends on your state and county. Some allow holding tanks where a drainfield can't be built, under conditions on size, alarms and truck access. Your local health department decides.
They cost in different ways. Septic costs the most up front and little to run. A holding tank costs little to set and keeps costing for every pump-out, so a larger tank pumped less often is usually the cheaper way to run one.
Yes. We place holding tanks with scheduled pump-out and run septic pumping programs across many locations. Call sales at (888) 588-2607 with the site and what it needs.
Tell us what the tank serves and how often you want a truck through the gate. Local providers do the pumping; we hold the contract, own the problems, and send one bill.
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Sources