Drainage plans for my house: why they matter.
You might think you'll never need a drainage plan for your home.
Until you do.
It usually starts like this: A builder turns up to dig foundations, or someone starts work on the garden. Then suddenly they hit a pipe. Or they block a vent. Or worse, they damage a private treatment plant or soakaway they didn't even know was there.
Knowing what's underground isn't optional anymore.
"Nobody told me there was a pipe there."
We hear this all the time from customers, builders, and even surveyors.
Private drainage systems are often unrecorded, especially in older or rural properties.
We recently worked at a house in Walton-on-the-Hill.
There were multiple downpipes, unclear direction, and a treatment plant buried deep with extended turrets.
The issue wasn't just depth. It was lack of clarity.
No one could confirm:
- Whether the tank was surrounded by concrete
- If it had been secured against popping
- Who installed what, or when
That's a real risk, especially with saturated soil and heavy excavation.
What a good drainage plan includes.
At ASL Limited, when we carry out a full drainage survey, we provide a detailed sketch.
It shows:
- Where the private drains run
- Direction of flow
- Access points and manholes
- Any tanks, treatment plants, or soakaways
- Shared or adopted systems (if known)
We often use a probe to track and mark the pipe direction across the property.
Then, we red-pen that onto a paper sketch, which we leave with the customer.
That way, anyone doing future work knows where not to dig.
One mark can save thousands.
We had a job in Cobham where a contractor was about to concrete over an access point.
We'd provided the homeowner with a marked-up plan six months earlier, they spotted the error and saved the job.
One red pen. One sketch. Thousands saved.
This isn't just about paperwork. It's about avoiding damage and delay.
Builders need to know, too.
Whenever builders are working on a project, we recommend:
- Giving them a copy of the drainage plan
- Warning them about any private systems, especially marked in red: no surface or roof water! We have a private system
- Asking them to avoid covering or redirecting existing gullies, soakaways, or tanks without checking
We've seen too many cases where an extension was built too close to a treatment plant lid, or where access to a pipe was permanently blocked.
All because "nobody saw it."
Not sure what's underground? We can help.
We offer simple on-site checks and full drainage surveys with clear, hand-drawn plans.
They're quick to produce and could save you a huge headache later.
📞 Call ASL Limited on 0800 181 684. Ask for a drainage plan with sketch. It's a small step that protects your home.
We cover Surrey, Berkshire, Hampshire, West Sussex and South West London.
Related services.
To learn more about how ASL Limited can help you understand your drainage system:
