14.2 Holding Tanks

14.2 Holding Tanks

Quick Answer: 248 CMR 10.09(1) lists holding tanks with interceptors and separators. The gallon numbers 10.09 actually prints for a holding tank are the no-sewer petroleum containment recipe: maximum two vehicle bays, minimum 60 gallons per vehicle, double-wall tank and pump rated for volatiles, leak sensor in the interstitial space, 4-inch inlet, 2-inch vent returned inside and independently through the roof, tested before service. The Board’s 05-29-2013 alternative-method policy still needs a variance before installation and sets the high-level alarm at 75 percent capacity. 10.09 does not publish a house-sewage holding-tank gallon table. Do not invent one. A 10.15(9) ejector sump that pumps into gravity drainage is not a pump-out holding tank.

PSI’s October 3, 2025 bulletin names Holding Tanks as one of five items in the separators cluster. Candidates lose those items by quoting an IPC “sewage holding tank” volume, by treating a basement ejector as a holding tank, or by discharging a garage containment tank to the city sewer because “it has a pump.” Independent OpenExamPrep teaching uses the 12/8/2023 10.09 text, 248 CMR 3.04, and the Mass.gov Gas/Oil Separator Alternative policy PDF. It is not a Board publication.

What 10.09 actually calls a holding tank

248 CMR 10.09(1) — interceptors, separators, and holding tanks shall be provided to prevent discharge of oil, gasoline, grease, sand, and other harmful or hazardous substances to building drainage, public and private sewers, DEP-governed systems, treatment plants, or other environmentally sensitive areas. No wastes other than those requiring treatment or separation shall discharge into any interceptor, separator, or holding tank.

That opening sentence is the exam’s first sort. A holding tank in 10.09 is a containment device for waste that must not go untreated into the drain. It is not a spare septic tank, not a 10.03 septic tank (which is designed to discharge liquid to a soil-absorption system), and not a 10.15(9) tightly covered, vented sump whose pumps lift sewage into the building gravity drainage system.

Sewage versus waste holding — keep the three pipes separate:

When is a holding tank allowed? When 10.09(1)(a)3 applies: Rules for Containment Systems — When Not Connecting to a Sewer System. If a public sanitary sewer is available, 248 CMR 10.05(15) (Chapter 11.2) still wants an independent building-sewer connection. A pump-out tank is not a field convenience for skipping that tap. If the site is DEP-governed, notice of the containment installation must be made to DEP before the plumbing permit (10.09(1)(a)3.a).

The only 10.09 containment volumes the code prints: for smaller installations involving a maximum of two vehicle bays, a pump connected to a double-wall tank, both rated by the manufacturer to hold volatile chemicals, meeting 10.09 Example 1:

1. Tank holds a minimum of 60 gallons per vehicle.
2. Tank has a liquid sensor to detect leaks.
3. Tank is vented through a roof.

Piping (10.09(1)(a)3.c):

• Minimum inlet 4 inch.
• Vent not less than 2 inch, returned to the inside of the building, and extended independently through the roof.
• Tank and piping tested before being put into service.
• Piping materials limited to extra heavy, service weight, and no-hub (cast iron, as 10.09 states for this containment piping).

Do not invent other volumes. 10.09 does not print 500-gallon, 1,000-gallon, or “one-day sewage flow” holding-tank sizes for dwellings. If a Board of Health authorizes a Title 5 tight tank for sewage where a soil-absorption system cannot be sited, that gallon figure comes from 310 CMR 15.00 and the approving Board of Health — it is not a number to memorize as 10.09. Unsewered grease already cross-references Title 5 in 10.09(1)(b)1.e; that is FOG on a septic site, not a license to guess a sewage tank.

Scenario. A New Bedford two-bay repair garage sits on a Title 5 lot with no municipal sewer. Floor drains that can see petroleum go to the 10.09(1)(a)3 double-wall containment tank: 120 gallons minimum (60 × 2), leak sensor, 4-inch inlet, 2-inch independent roof vent, DEP notice before the plumbing permit, cast-iron containment piping, test before use. The toilets still go to the Title 5 tank, not into the oil containment tank. No wastes other than those requiring treatment or separation enter the holding tank — that sentence forbids mixing soil-stack sewage into the oil box.

Scenario (illegal). A Lowell shop on a city sanitary sewer wants a 60-gallon drum under the floor drain “as a holding tank so we do not buy a separator.” 10.09(1)(a)2 is the sewer-connected path (Example 2 separator, Product-accepted separator, or PE-designed separator). Containment 10.09(1)(a)3 is when not connecting to a sewer. The drum is not 10.09.

Alarms, venting, pumping, and Board permission

Alarms 10.09 actually prints. The coded two-bay containment tank must be equipped with a liquid sensor to detect leaks (interstitial / between walls). That is a leak alarm path, not a “how full is the tank” float unless the manufacturer’s listing adds one.

Alarm the Board policy adds. Mass.gov Gas/Oil Separator Alternative PDF — Board Policy, Alternative Method to Meeting the Requirements of 248 CMR 10.09, enacted 05-29-2013 — diagrams a double-wall vented storage tank with a liquid sensor in the space between the two walls, a liquid-level sensor with alarm set for 75 percent capacity, a pump rated for the installation, vent through the roof, sump pit, check valve, and ball or gate valve. Criteria on that PDF:

• Maximum of two vehicles/bays
• Size the double-wall tank using a minimum of 60 gallons per vehicle
• Properly filed variance must be approved by the Board prior to installation
• No engineer stamp required
• Pump and tank do not require Product-acceptance
• Allowable for new or retrofit

Read the policy as an alternative method that still needs 248 CMR 3.04 variance approval before work. The 12/8/2023 code already describes a two-bay containment tank; the policy is the Board’s drawn alternative (75 percent high-level alarm, listed accessories, Product-acceptance waiver for that pump and tank). Do not tell the exam that Product-acceptance is never required for every holding tank in the Commonwealth — that waiver is this policy’s sentence, after a granted variance.

Venting. Containment: 2-inch minimum, back inside, independent through the roof (10.09(1)(a)3.c.ii). The tank itself is vented through a roof. Separator chamber and outlet vents (next section) are 4-inch and labeled; do not shrink those to 2 inch because a holding-tank stem mentioned 2 inch. Floor-drain vents on petroleum systems stay independent of sanitary DWV (10.09(1)(a)4).

Pumping. A containment holding tank has no legal overflow to the sewer. The owner’s hauler pumps it. The 2013 drawing shows a rated pump, check valve, and isolation valve so the sump can be emptied into the double-wall tank without backflow. Grease interceptors (14.1) are cleaned by the owner or agent under health rules; that is FOG pumping, not sewage. 10.15(9) ejectors pump to gravity sanitary — different machine, different exam item.

Board / Special-permission (248 CMR 3.04). Three doors, not one slang word “ask the Board”:

1. Product-acceptance — a product may be installed under 248 CMR after the Board votes; do not install before that vote.
2. Variance — alternative method, material, system, or product for one instance at one location when the Board finds unusual circumstance or hardship; work subject to a variance does not begin before the Board grants it (with the regulation’s limited after-the-fact exception).
3. Special-permission — when a provision of 248 CMR requires Board permission before using a product, system, design, or method because safety is of special consideration; request in writing and appear if the Board asks.

A sewage pump-out tank that 10.09 does not describe is not something you invent a gallon for and install. You either stay on 10.05(15) / Title 5, stay on 10.15(9) if the problem is elevation, or you file under 3.04. The exam stem that says “Special-permission has not been granted” is telling you the unlisted holding tank is illegal.

Do not import 10.13 pH audio/visual alarms onto a 10.09 oil holding tank, and do not import 10.15 Table 5’s 20 GPM ejector onto a containment tank. Those numbers belong to other chapters.

Official resources

• 248 CMR 10.09 (Cornell LII) — 10.09(1) opening and 10.09(1)(a)3 containment / Example 1
• Gas/Oil Separator Alternative (Mass.gov PDF) — 05-29-2013 variance method, 75% alarm, 60 gal/vehicle
• 248 CMR 3.00 Product, Design, and Testing Standards (Mass.gov) — Product-acceptance, variance, Special-permission
• 248 CMR 10.15(9) Sumps and Ejectors (Cornell LII) — gravity discharge, not a holding tank
• 310 CMR 15.00 Title 5 (Mass.gov) — unsewered overlay named in 10.09