Macerator (Saniflo) toilets: pros, cons and where you can fit one

How a macerator toilet works

The toilet flushes into a unit behind or beside the pan instead of straight into a large soil pipe. When the unit senses water, a motor turns cutting blades that break the waste down, and a pump pushes it along a small-bore discharge pipe, usually 22 mm to 40 mm depending on the model, to a soil stack or drain.

Because the waste is pumped, the pipe can run upwards and a long way sideways, which a gravity toilet cannot do. How far and how high depends on the model, and the manufacturer's tables for vertical lift against horizontal run have to be followed. Many units also take the waste from a basin or shower, so a whole small shower room can run through one pump. Some models are made to sit inside a wall frame in the same way as a hidden toilet cistern, provided there is a panel for servicing. For how a macerator compares with gravity toilets, see our guide to the types of toilets.

The advantages

For many London homes, particularly terraces and conversions where the only stack is at the back of the house, a macerator is what makes a second toilet possible at all.

• You can put a toilet where the soil stack is out of reach, including below the level of the drain
• Small-bore pipework fits inside stud walls and floor voids, with far less building work than a new 110 mm soil run
• Adding a second toilet can raise the value and practicality of a family home or a loft conversion
• One unit can serve a toilet, basin and shower, which keeps a small ensuite or utility-room WC simple
• Work is often quicker and less disruptive than breaking into walls and floors to extend the stack

The drawbacks

None of these rules a macerator out, but they are the reason it is best as a second or third toilet and not the one a whole household relies on.

• Noise: the motor runs for several seconds after every flush and can be heard in nearby rooms
• Electricity: no power means no flushing, so a power cut takes that toilet out of use
• Blockages: wet wipes, sanitary products, cotton buds and too much paper can jam or damage the blades and pump
• Maintenance: London's hard water scales the unit, so periodic descaling with a product the manufacturer approves is needed
• Repairs: pumps, switches and seals wear, and a failed unit can back up into the pan or connected shower
• Smells, if the vent or seals fail, or if the discharge pipe has dips where waste settles

What the Building Regulations say

Approved Document H, which covers drainage in England, allows WCs with macerators and small-bore pumps, but only where the building also has access to a WC that discharges to the drain by gravity. It also expects the unit to be a type made and approved for that job. In practice, a macerator can be your loft or basement toilet, but it should not be the only toilet in the home.

The electrical side matters too. The unit needs a suitable fused connection, and in a bathroom the position of that connection is governed by the wiring regulations for wet areas. That part of the job should be done or checked by a qualified electrician.

If you live in a flat, the discharge pipe may need to join a shared soil stack. Check your lease and ask the freeholder or managing agent before you plan the route; our guide on what to check before altering plumbing in a leasehold flat explains what usually needs permission. If the space you have in mind is a toilet under stairs, our guide to that layout covers the door, basin and ventilation rules as well as the drainage choice.

What makes a macerator install last

Many macerator problems trace back to the installation rather than the product. A few details make the difference between a unit that runs quietly for years and one that keeps failing.

The discharge pipe should rise straight away if it has to rise at all, then fall steadily to the stack with no dips or sags where waste can collect. Bends should be kept to a minimum and made with swept fittings. The unit has to stay accessible so it can be serviced without taking the bathroom apart, which means a removable panel rather than tiling it in. Where the unit takes a shower, the shower waste needs a proper trap before it enters.

After that, it comes down to use. Put a clear note in the room: toilet paper only. Wipes labelled flushable are still not suitable for a macerator.

Planning a macerator toilet or fixing one

Loyal Plumbers installs toilets and small bathrooms as part of our bathroom fitting work across London and everywhere inside the M25, including macerator WCs where a gravity connection is not practical. We look at where the stack is first, because a short gravity run is usually the better long-term option when it is possible, and we plan the discharge route and access before any wall is closed up.

If you already have a macerator that runs on, will not pump or is backing up, stop using the connected toilet and shower and see our guide to macerator toilet faults before calling. To plan a new one, call us or send an enquiry with the room, where the nearest soil pipe is and what you want the unit to serve.