Macerators
Introduction
Put simply, a macerator is a waste disposal unit combined with a pump, which is able to reduce solid waste to liquid and to pump the waste against gravity.
The pumping system is designed for the disposal of normal organic waste product, water or paper along a small bore pipe to eventually join the main sewage pipe for the building.
Ordinarily a toilet (wc suite) is positioned next to the main sewage pipe for the building to ease the removal of waste matter directly from the property. The building regulations specify that the sewage pipe must pass vertically immediately from the wc to the sewers.
A sewage pipe is rather large though, and in situations where it is not possible to place a bathroom immediately over the existing pipe, it is often not appropriate to add an additional pipe to the property as it will invariably need to pass through at least one room, and the floor at ground level will need to be pulled up to locate the sewer. In these circumstances a macerator unit allows for the inclusion of a toilet.
- You should not flush nappies, wet wipes or sanitary towels since these items can cause blockages.
Common applications
Macerators allow for a bathroom or utility room to be created anywhere within a property, even far away from the sewage pipe.
Most commonly found in a bathroom within a loft conversion, they can also be used in domestic kitchen/utility situations. Their usage often means there is no need for costly and difficult masonry work simply to add an additional toilet (wc suite) to a property.
- The units operate at a noise level of approximately 55 decibels (subject to installation and location)
- Installed and used correctly, the unit is very reliable and needs no servicing.
- Can be used in situations where unit is more than 10 metres from sewage pipe*
- Macerator units usually do not function correctly when fitted to syphonic pans.
- Will easily become blocked if the wrong items are disposed of via the wc.
- Often costly to repair
* You should increase the pipe size from 22mm to 32mm from the 10 metre point onwards.
- Macerators are not intended to replace kitchen waste or sanitary waste disposal units.
- The pipe-work should have a 1% (1 cm in every metre) fall along its length.
Fitting a macerator
- To avoid dipping and build up of residual water and subsequent blockage all discharge pipework should be supported in accordance with manufacturers specifications and installed with a minimum 1:100 fall to the soilstack.
- The units generally accept waste water by gravity. They do not suck in water. All pipework into the units must have a positive gravity fall (1:40).
- All pipework should be either copper or CPVC conforming to BS7291.
- Do not use flexible or push-fit pipework.
- The unit should be easily accessible and removable in the event of maintenance being required.
- For long horizontal runs where 22mm pipework is used this should be increased to 32mm after approximately 12 metres to eliminate risk of trap siphonage.
FAQs
- In what circumstances do Building Regulations allow installation of a macerator?
The Building Regulations: Part G permit the installation of a macerator only if there is access to a gravity discharging WC. - Who is permitted to install a macerator?
Building Regulations: Part P state that if an electrical installation involves running new cable work in a kitchen or bathroom, then it must be reported to Building Control and carried out by a competent person registered with the Electrical Regulating Authority, or checked by someone who is registered with them. - What kind of bend can I install on the discharge pipework?
You must either use a smooth pulled bend or 2 offset bends together to get a smooth radius.
Further information and useful links
Site Pages
Featured Articles