The answer to your question is easy...Code only allows the saniflow system where the desired fixture location is below the DWV system and a drain line cannot be achieved by gravity flow..

If it can be done by gravity flow that is the way you have to do it regardless of cost.

Thanks lazypup.

I'm a total novice with respect to plumbing, so I'm not sure what you mean when you say, "DWV system". If it helps: in our basement, the big white PVC drain pipe is half way up the basement wall, and exits the house at a slightly lower height than where the drains from above merge with that which is in the basement.

So, if the toilets, etc in the basement would be below the drainage pipe, would that tell me that Saniflow should be used?

Thanks...

"DWV system"

Drain, Waste, Vent.

Are you on municipal sewer or septic? If you're on septic, you'll want to check if there are any special requirements for adding that type of pump. Even if there aren't, I'd recommend adding extra tankage with filters for settling of the particles to keep the drainfield from clogging prematurely.

Okay, let me take this in order:

As was previously mentioned by Brickeyee,

DWV is an abreviation for the Drain, Waste & Vent system.

Under normal circumstances the DWV system is pitched downwards from the furthest fixture to the point where the house sewer line attaches to the municipal sewer or the septic tank and that system operates by gravity flow.

In some instances were the municipal sewer is relatively deep and the setback distance from the municipal sewer to the structure is not too long the house sewer may enter the structure at a point below the basement floor and normal drain fixtures can be installed in the basement, however in instances such as yours where the house sewer enters the structure at a point which is higher than the basement floor gravity flow cannot be achieved simply because "The stinky stuff don't flow uphill." In fact, when there is a long setback from the municipal main to the structure the plumber has to compute the drain elevations and it is the plumber who determines what the minimum elevation of the ground floor may be to maintain gravity flow.

In circumstances such as yours the house sewer enters the structure at some point above the basement floor so we can achieve normal gravity flow for the first floor and all subsequent floors above that, but not the basement floor so generally no drains are installed in the basement.

If a drain is required in the basement we must then install some type of "sewage lift station" to physically pump the discharged effluent up to the gravity flow lines.

In essence a lift station is a water tight/air tight sump with a pump inside. The drains all discharge into the pit, then the pump lifts the effluent up to the gravity line. Generally that is easy when installed during construction and before the basement slab is poured, but when retrofitting an existing structure it can be rather difficult and extremely expensive.

Sani-flo offers another option. They build a self contained lift station that has a pad that extends through a bathroom wall so the pump assembly remains outside the bathroom but the pad extends through the wall and a watercloset (toilet) is installed on the pad inside the bathroom. The Sani-flow systems also allow additional inlets so you can attach a lavatory sink, washer standpipe or laundry sink to the sani-flow system. (A tub or shower can also be discharged into a sani-flow unit but you either have to raise the floor of the bathroom or cut the concrete and install a recessed sani-flow unit below the floor.

It must be mentioned here that when you install a saniflow unit you will also have to install two separate 1-1/2" vent lines. The fixtures must be vented in the conventional manner and that vent line may be combined with other vents in the house providing the point of attachment is a minimum of 6" higher than the flood level rim of the highest fixture served by the vent you are attaching to. The sani-flo unit itself, or any other type of sewage ejector lift station must also have a dedicated vent that runs through the roof. It may not be combined with any other vents.

Now in regards to modifications to a septic system. That is totally false. The discarge line from the sani-flow is a 2" line and it is required to dischage into a 3" or 4" line. Now, while the velocity of flow is much greater in the sewage ejector discharge line, the actual volume that is discharged at any given time is relatively small, on the order of about 6 to 8 gallon max between cycles. A 3" line has approximately twice the volume of a 2" line and a 4" line has approximately four times the volume so teh volume is quickly broadened out and slows to standard gravity flow velocity long before it reaches the septic tank.

That wasn't my point. The concerns is with the extra fine particles in suspensions due to the pump action. In that case you want extra tankage for settling to achieve quiescence in the tank, better if extra effluent filters are installed in the tank(s) outlet tee.

That seems to be your concern but I don't know of anyone in the business that shares your concern except those who are trying to sell the filters...

First off, a septic tank is sized to contain an average of three days or effluent discharge from the structure and given that the average discharge is 300gal/day, the tanks are typically between 900 & 1200gallon.

The amount being discharged from that pump would seldom exceed 30gal in a day, and only an extremely small portion of that would be suspended solids that are macerated.

Next, the septic tank is divided into two chambers by a baffle so the discharge from the pump would be entering about 6" above the level in the first chamber and as the liquids flow in the suspended materials are generally suspended by the sludge layer on the top of the tank. Those suspended solids remain in the sludge layer until the break down into a liquid state and settle towards the bottom of the tank where they pass through the baffle and on into the digestor portion of the tank. There simply is no way that the fine particles in the waste entering the tank will go straight to the outlet tee.

Taking this to the next level, not all sewage pumps are macerating pumps, in fact, very few are.

Well I must be mistaken when I see that lack of settling in two tanks in serial connection when sewage lift pumps are used without a settling tank prior to the pump.