Buying a property that sits below the sewer? What to check

Most pre-purchase advice covers the roof, the stumps and the wiring. Almost none of it mentions how the waste actually leaves the property, which is fine in a suburb where it leaves by gravity and less fine on ground that falls away below the sewer main.

This is not a reason not to buy. Plenty of very good houses here are on pumped systems and have been for decades. It is a reason to know before you sign, because it changes the running costs, the maintenance and what happens in a blackout.

The short answer

Find out before you buy whether the property drains by gravity or by pump, and if it is a pump, whether it is yours or Sydney Water's. A pump inside the boundary is the owner's to power, service and eventually replace, and none of that appears in a standard contract.

1. Ask the agent directly, and get the answer in writing
2. Look for a pump well, a control panel or an alarm
3. Check the sewer service diagram for the property
4. Establish whether the pump serves one property or several
5. Have it inspected rather than assumed

On this page

1. Why some blocks cannot use gravity
2. How to tell before you buy
3. Whose pump is it
4. What it means to live with
5. Renovating on a pumped block
6. Questions to actually ask

1. Why some blocks here cannot drain by gravity

Sydney's sewerage was built to run downhill. That works everywhere the ground obliges, and it does not work where a property sits lower than the main it is supposed to discharge into. On the low-lying ground around the harbour that situation is common enough that Sydney Water has been solving it with pumps since the 1920s.

The fix is straightforward in principle. Collect the waste at the low point, then lift it back up into the gravity system through a pressurised line. The complication is only that a lift needs a machine, and a machine needs power, servicing and, one day, replacing.

2. How to tell, before you own it

Ask the agent whether the property is on a pumped sewer system, and ask for the answer in writing. It is a reasonable question and a vendor who knows will simply tell you. If nobody knows, that is itself worth noting.

Then look. A private pump usually shows itself: a lid or access chamber somewhere low on the block, a small control panel or isolator on an external wall, sometimes an alarm unit near the meter box. None of these are hidden, they are simply not the sort of thing most buyers are looking for.

Sydney Water can supply a sewer service diagram for a property, which shows the drainage layout and where it connects. It is the document most likely to answer the question properly, and it is worth having regardless.

3. Whose pump is it, and why that is the important question

Sydney Water owns and operates the low-level pumping stations that serve streets and pockets of a suburb. Those sit on public land, and if one of them fails it is not the homeowner's problem to solve or fund.

A pump inside a private boundary serving a single property is a different thing. The owner powers it, services it and replaces it. That is not a catastrophe, it is simply a cost that exists and that most buyers have not budgeted for because nobody mentioned it.

On a shared arrangement between a handful of properties, ask who currently maintains it and how the cost has been split historically. An answer that begins "nobody has really had to" is worth following up.

4. What a pumped property is actually like to live with

• Power matters more. No power means no drainage, and the storage between the house and the well is small. Households on pumps tend to learn this once.
• The flush rules are stricter. Wipes, fat and fibrous material cause mechanical failures rather than blockages.
• Failure is abrupt. A gravity drain warns you by slowing down. A pump works perfectly until it does not.
• It is maintainable, which a buried drain is not. The float, the non-return valve and the impeller can all be checked before they strand anybody.

That last point is genuinely the upside and it is worth weighing properly. A buried gravity line offers almost nothing to inspect until it fails. A pump can be put on a schedule.

5. If you are planning to renovate

Adding fixtures adds volume, and on a pumped system volume is the thing the equipment is sized for. A second bathroom or a new laundry is not automatically a problem, but it is a question worth asking before the plans are finalised rather than after the slab is poured.

The same goes for anything that changes levels on the block. Where the fall is already marginal, a new floor level or a fresh run of drainage can change what has to be pumped and what can still gravitate.

Any new sanitary drainage work is licensed work and generates paperwork. Keep it with the house documents; the next owner will be asking the same questions you are asking now, and a property that can answer them is easier to sell.

6. The questions worth asking out loud

• Is the property on a pumped sewer system, or does it drain by gravity?
• If it is pumped, is the pump inside the boundary or is it Sydney Water's?
• How old is the pump, and when was it last serviced?
• Is there an alarm, and does it work?
• Has the property ever backed up, and what was done about it?
• Is there a sewer service diagram available?

None of these are awkward questions. They are the ones a buyer who understands the ground asks, and the answers cost nothing to obtain before you commit.

The short version

• Some low-lying blocks here cannot drain by gravity and are served by a pump instead.
• Ask before you buy, and get the answer in writing rather than assuming.
• Sydney Water owns the street pumping stations. A pump inside the boundary is the owner's.
• A pumped property costs a little more to run and fails more abruptly, but it can be serviced.
• Adding fixtures adds volume, so raise it before the renovation plans are final.