How Long Will a 750 Gallon Septic Tank Take to Fill Up?

Septic tanks are designed to collect raw sewage and solid waste for bacterial digestion. Any non-digested materials will float to the surface as scum layer or settle to the bottom as sludge.

Avoid placing chemical drain openers, cooking fats, coffee grounds, bones, paper towels or cigarette butts into the sewer as this could disrupt bacterial activity and pollute groundwater supplies.

Size of the Tank

Septic tank sizes are determined by local regulations based on the number of bedrooms in a house and water usage. A typical septic tank is typically 750 gallons; during normal functioning, waste from all drains in the home are sent directly into this tank for treatment and reduction, then sent down each drain into it until finally reaching the septic tank at which point liquid, cooking oil, and any thick sludge forms at the bottom of it all.

Once solids have been processed, any remaining liquid should be absorbed by an absorption field and the septic tank should be emptied when its level reaches 8-12 inches below maximum capacity.

If the septic tank is not regularly pumped out, it can overflow, which is harmful because it indicates the failure of its system and releases pathogens into the environment. Furthermore, this violates local environmental laws.

Therefore, having your septic tank pumped at regular intervals is vitally important. Not only will this prolong its life but it will also protect both drain fields from being compromised by excess sewage as well as prevent back up into homes from the septic tank itself.

Number of Bedrooms

A septic tank serves as the first stop for waste in your home, collecting sewage from bathrooms and appliances such as laundry machines, kitchen sinks and toilets before being treated by bacteria to remove harmful materials before it moves through drain fields to be absorbed back into the earth. Tank sizes typically accommodate how much wastewater will be produced each day by each home – typically 1,000-gallon tanks serve three bedroom houses while larger models may also be utilized by apartment complexes or community tanks.

Calculating the number of bedrooms in your home when selecting an appropriate tank size is a useful method for getting a realistic picture of how many people will be living there and their daily volume of water usage. Selecting an adequate tank initially can save money over time by eliminating costly replacement needs later on.

Installing a septic system correctly means choosing the appropriate tank size; an incorrectly sized tank could result in costly repairs or even the replacement of your entire septic system altogether, so working with an experienced professional is vital to finding an ideal solution for both home and budget.

Water Use

Water consumption by you and others in your household plays a significant role in septic tank capacity. Showers, laundry, dishes and cooking produce wastewater which flows into the tank where liquids and solids pass through a filter toward leach fields for disposal. As its capacity decreases due to being filled up with sludge and scum build-up, effluent rates from liquid effluent are released into soil absorption fields (or soakaway beds as it’s known in some countries) reduces.

Sollte the tank reach capacity and solid waste begins to overflow into the drainfield, the septic system could collapse and cost thousands in repairs and replacement costs.

Even if your septic tank doesn’t reach capacity, pumping should still be performed regularly to protect beneficial bacteria and keep too much sludge from building up and damaging the drainfield.

Professionals typically suggest having your septic tank pumped every year and a half. If your household doubles in size, additional pumping may be required more frequently. Furthermore, having it inspected more often – at least once annually – will allow you to detect signs that it needs pumping sooner than anticipated.


As part of homebuilding or purchasing existing properties, it is advisable to obtain the recommended septic tank size. This will prevent having an over-full septic system which could require costly repairs in the future and ensure its longevity for many years to come.

Pumping your septic tank when its sludge layer exceeds that of the scum layer is highly recommended, since leaving it empty too long may allow raw sewage to flow directly into the drain field and cause serious clogs and problems; you could even require installing an entirely new system, which can be quite costly.

Septic tanks have been designed to facilitate bacterial digestion by encouraging particles that are heavier than water to settle at the bottom, creating sludge. Meanwhile, particles lighter than water may float to the top, creating the scum layer.

However, some factors can increase the accumulation of solid waste in septic tanks. For example, using a garbage disposal can increase solid waste deposits to around 50%; similarly pouring grease or non-biodegradable types of solid waste down drains also adds to its accumulation in septic tanks.