Dosing Chambers and Pumps

(1) A dosing chamber shall be required for any system that is not designed to discharge by gravity to the soil absorption system, for any system that is designed for the intermittent discharge of septic tank or recirculating sand filter effluent, and in conjunction with pressure distribution pursuant to 310 CMR 15.254(2) for any system with either a design flow of 2,000 gpd or greater, or where multiple soil absorption systems are proposed. (2) All dosing chambers shall have an emergency storage capacity above the working level equal to the daily design flow of the system, or standby power, and shall be equipped with sensors and alarms to protect against high water due to failure of the pump or pump controls. It is advisable to provide some emergency storage even if an on-site emergency generator is provided. The volume below the working level shall include an allowance for the volume of all drainage which may flow back to the chamber when pumping has ceased. (3) The volume of the dosing chamber between pump operating levels shall be adequate to assure the entire soil absorption system is dosed each cycle in accordance with the required number of cycles per day. (4) Construction and materials of dosing chambers shall be in accordance with 310 CMR 15.221 and 15.226. (5) All dosing chambers shall be designed and constructed to withstand a minimum H-10 loading. Any dosing chamber installed where there is the potential for vehicles or heavy equipment to pass over it shall be designed to withstand an H-20 loading. Dosing chambers shall be equipped with one manhole with a minimum opening of 20 inches with a readily removable watertight cover of durable material. The access cover shall be located at final grade. (6) Every dosing chamber, except for systems serving two dwelling units or less, shall be equipped with two pumps the discharge lines of which shall be valved to allow dosing of the entire soil absorption system by either pump. (7) Pumps shall be installed in accordance with the manufacturers and the designer’s specifications. (8) Pumps shall operate in the following sequence: (a) pumps off (b) primary (lead) pump on (c) backup (lag) pump on and alarm on (d) pumps must alternate. (9) All pumps must be equipped with a high water level alarm located in the building served which is powered by a circuit separate from the circuit to the pumps. (10) An effluent tee filter or equivalent technology approved by the Department is required prior to or within a dosing chamber. (11) All dosing chambers shall be watertight. (12) All dosing chambers proposed to provide standby power instead of emergency storage capacity shall include a permanently installed on-site emergency generator that shall automatically switch on in the event of power failure.