What is a drainage and water search?

A standard conveyancing search — usually the CON29DW — bought from the water company when you purchase a property. It confirms whether the property is connected to the public water supply and public sewers, shows nearby public sewers on a map, and covers things like who bills the property. Nearly every purchase includes one.

What does the drainage search show if the house has a septic tank?

Essentially one crucial fact: that the property is NOT connected to the public foul sewer. That single line is what tells your solicitor a private system exists. The search does not tell you what the system is, where it is, what condition it's in, or whether it complies with the General Binding Rules — all of that has to come from the seller's answers and, ideally, a survey.

The search says the property isn't connected to the public sewer — what should happen next?

Your solicitor should raise enquiries: what type of system is it, where is the tank and drainage field, when was it last emptied, is there a maintenance or service record, does it discharge to ground or a watercourse, and does it meet the 2020 General Binding Rules. The seller answers via the property information form and follow-up enquiries. For anything older or undocumented, a septic tank survey before exchange is money well spent.

Can a house be sold if it's not connected to mains drainage?

Yes — hundreds of thousands of UK homes run on septic tanks and treatment plants. What matters in the sale is that the system is identified, its compliance position is understood, and any problems are priced in. Deals run into trouble when the private system only gets attention at the last minute, not because off-mains is unsellable.

Does the drainage search check General Binding Rules compliance?

No. The water company knows what it's connected to; it knows nothing about a private system's compliance. General Binding Rules compliance is established from what the system is and how it discharges — which is exactly what the free compliance checker on this site walks through, and what a survey confirms physically.

The drainage and water search when the house is off mains

Every property purchase includes a drainage and water search — usually the CON29DW, bought from the water company. For most buyers it’s a formality that confirms the house is on mains.

For an off-mains property, it does something different and more important: it’s usually the moment the buyer’s side discovers a private sewage system exists. And that’s roughly where its usefulness ends — which is the part buyers misunderstand.

What the search actually tells you

The CON29DW answers questions about public infrastructure: is the property connected to the public water supply, is it connected to the public foul and surface-water sewers, where do the nearest public sewers run, who bills the property. In Cornwall the answers come from South West Water’s records.

For a house on a septic tank, the key line is a negative: “not connected to the public foul sewer.” One line, and everything about the property’s drainage becomes a private matter between you, the seller, and — since 2020 — the Environment Agency’s rules.

What it cannot tell you

The water company has no records of private systems. The search will not tell you:

What the system is — septic tank, treatment plant, cesspit or a private pumping station
Where it is — including whether the tank or drainage field sits on someone else’s land, or serves more than one property
What condition it’s in — age, last empty, whether the drainage field is failing
Whether it complies with the General Binding Rules — the search doesn’t ask and the water company couldn’t answer

So a clean search on an off-mains house is not reassurance. It’s a starting gun.

The enquiries that should follow

Once the search shows no public connection, the buyer’s solicitor should establish, through the property information form and follow-up enquiries:

What is the system, and where? Tank, plant or cesspit; location of tank and drainage field; access for emptying.
Whose is it? Solely owned, or shared — and if shared, what the arrangement is.
The paperwork. Emptying receipts, and for a treatment plant the service records — the General Binding Rules require maintenance to the manufacturer’s instructions, so records are the compliance evidence.
The discharge. To ground via a drainage field, or to a watercourse — the rules differ, and a septic tank discharging straight to a watercourse has needed upgrading since 2020.
Any history. Smells, backing up, boggy ground over the field, Environment Agency contact.

Note what the seller can’t provide: there is no official compliance certificate to ask for. The evidence is the system itself plus its records — which is why, for anything old or undocumented, a septic tank survey before exchange is the single best £250–£500 a buyer of an off-mains house can spend.

If the answers come back bad

A non-compliant or failing system doesn’t kill the purchase — it starts a negotiation about who pays, informed by what replacement actually costs. What loses buyers money is finding out after completion, when the responsibility became theirs at the moment they took ownership.

Two-minute head start

Before the enquiries even come back, the free compliance checker tells you what the 2020 rules require of the system described in the particulars — so you know which answers matter before you’ve paid for them.