CLEARMASTERS
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The basics
What is a holding tank?
A holding tank is a sealed tank that stores wastewater or other liquids until they can be taken away. You'll find them wherever there's no drain to connect to: site welfare units, remote buildings, wash-down areas, event sites and many more.
We can empty portaloos and welfare units on the same site visit, and remove oily or contaminated water where that’s what the tank holds.
We do this work across Surrey, West Sussex, East Sussex, Kent, Hampshire and London, with tankers and engineers in each area most days.
Like a cesspit, a holding tank has an inlet but no outlet, so nothing drains away. When it's full, it needs emptying by a tanker.
We empty holding tanks of all sizes, from a single tank at the end of a garden to large tanks on commercial and industrial sites, as a one-off, on a regular schedule or in an emergency.
Why us
Why use Clearmasters for your holding tank?
The right equipment
High-powered vacuum tankers from 2,000 to 4,000 gallons, with the hoses to reach tanks well away from the road.
Trained engineers
Experienced engineers who know how to empty tanks safely and cleanly, with minimal disruption to your site.
Emptying on your schedule
One-off visits, regular schedules planned around your site, or 24/7 call-outs when you need them.
Paperwork sorted
A waste transfer note every time, so you have a record of where your waste went.
Where it goes
Where are you taking my wastewater?
Once we've emptied your tank, we take the waste to a licensed facility to be treated and disposed of properly, in line with the regulations.
As the producer of the waste, you have a duty of care to make sure it's handled by a registered carrier and taken somewhere authorised to accept it. The waste transfer note we give you is your proof that you've done exactly that.
Signs your tank needs emptying
- The high-level alarm or gauge showing full
- Slow drainage from the connected toilets or sinks
- Bad smells from the tank or its vent
- Wet ground around the tank
- It's been longer than usual since the last empty
On the day
What happens when we empty your holding tank
We plan the visit
Tell us the tank size, what's in it and how to get to it, and we'll send the right tanker at a time that suits your site.
We empty the tank
We pump out the liquid and any sludge, and can wash the inside of the tank down if it needs it.
We take it away properly
Your waste goes to a licensed facility to be treated or disposed of in line with the regulations.
You get a waste transfer note
Your record of where the waste went, for your files and your duty of care.
Why Clearmasters
Why choose Clearmasters?
Whether it's one tank or a whole site, you'll get a friendly office team who plan the work around you, and engineers who do the job properly.
Ask us a questionAlways on hand
Routine visits booked at a time that suits you, and 24/7 call-outs when something goes wrong.
Advice from people who know
Our office team can talk you through your system, your options and the rules, or simply get you booked in.
Trained, friendly engineers
Our engineers work with minimal disruption and are happy to answer any questions while they're with you.
Regular schedules
Set up regular emptying and we'll book you in before your tanks fill up.
What our customers say
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Scores as of September 2026
Questions answered
Holding tank FAQs
How often should a holding tank be emptied?
It depends on the size of the tank and how quickly it fills, which varies a lot from one site to the next. Some tanks need emptying weekly, others a few times a year. Once we know your tank, we can recommend a schedule that means it never overflows.
What are the signs my holding tank needs emptying?
Slow drainage from connected toilets and sinks, bad smells from the tank or its vent, a high-level alarm or gauge showing full, or wet ground around the tank are all signs it needs emptying straight away.
What does your holding tank emptying service include?
We empty the liquid and sludge using a vacuum tanker, wash the inside of the tank down if needed, take the waste to a licensed facility and give you a waste transfer note for your records.
Will emptying the tank interrupt my site?
We plan the visit around your site to keep disruption to a minimum, and can work early or out of hours where that helps. We'll confirm access and timings with you before we arrive.
Why is regular emptying important?
It stops the tank overflowing, which can pollute the ground and shut your facilities down. It also stops sludge building up, which makes the tank easier to empty and helps it last longer.
What should I prepare before you arrive?
Please make sure we have safe access for the tanker and crew, the lids or hatches are unlocked and clear, and let us know the tank size and what's in it. Tell us about any site rules or inductions in advance.
Got a different question? Call 03333 233566 or send us a message.
Related services
Fully accredited & compliant
We're independently vetted and certified so you can trust who you're letting onto your site.
SafeContractor
Health & safety pre-qualification accreditation, verifying our processes meet recognised safety standards.
RISQS
Railway Industry Supplier Qualification Scheme — approved to work safely within the rail industry supply chain.
Achilles UVDB
Utilities Vetting Database membership, confirming we meet the utilities sector's supply chain standards.
Trading Standards Approved
Vetted and approved under the local authority's trusted trader scheme for honesty and fair dealing.
NADC Member
Members of the National Association of Drainage Contractors, the UK trade body for the drainage industry.
Registered Waste Carrier
Registered with the Environment Agency, so your waste is handled and disposed of fully within the law.