Macerators in a domestic situation are used when transferring bathroom and sink waste to the existing waste pipes is difficult due to either the distance or the height between the source and the existing soil disposal system as conventional pipes require to be fitted at an angle/drop so that gravity moves its contents. In large properties, macerators are often used to pump horizontally where laying a 100mm diameter soil pipe across three or four rooms would be both unsightly and expensive. Macerators are usually placed behind the WC but be careful as not all toilets have the space behind them at the base so check the measurements carefully. The way they work is to churn up solids and pump them at pressure down the pipework which is thinner than convention soil pipes. There are other models such as toilet pans with built in macerators which can look more minimalist and also be space saving.
Other models include ones that pump basin, shower, bath and bidet wastes as well as ones that can handle combinations of these different feeds. Access is normally required for servicing so make sure they have access hatches etc. All require an electrical supply.