A slow draining toilet in a gym or coworking washroom rarely stays a minor problem. When the bowl fills and empties gradually, the next few flushes can overflow onto the cubicle floor, and in a busy washroom that can happen within the hour. This guide explains how to unblock a slow draining toilet safely, what your cleaning team should and shouldn’t do, and when a commercial drainage engineer is the better option.
What Causes a Slow Draining Toilet in a Busy Washroom?
In most cases the toilet is partly blocked rather than fully blocked. Water can still get past the obstruction, but slowly, so the bowl empties over several minutes instead of seconds.
In shared washrooms the most common cause is material that shouldn’t be flushed. Thames Water clears 75,000 blockages from its sewer network every year and names wet wipes as the number one cause. Its research also found that wipes labelled “flushable” or “biodegradable” can still block pipes and sewers. In gyms and coworking spaces, wipes, sanitary products, paper towels and large amounts of toilet paper all end up in the same pipework.
Less often, the cause sits further down the system: a build-up in the branch pipe shared by several toilets, a partial blockage in the soil stack, or a problem in the underground drain.
Toilet Water Rises Then Slowly Drains: What It Tells You
When toilet water rises then slowly drains away, the question to ask is how many toilets are affected.
If only one toilet is slow, the blockage is most likely in that toilet’s trap or the short pipe behind it. This is usually something your team or an engineer can clear quickly.
If several toilets on the same floor or run are slow, or if flushing one toilet makes water rise in another toilet, a floor gully or a shower tray, the blockage is probably in shared pipework further along. Plunging individual toilets won’t fix that, and repeated flushing can push waste back up into the washroom.
How to Unblock a Slow Draining Toilet Safely
For a single slow toilet, a trained member of your cleaning or maintenance team can try the following:
- Take the cubicle out of use and put up an out-of-order sign so nobody flushes it again.
- Wear gloves and eye protection, and put absorbent material around the base of the pan in case of splashback.
- Use a flanged toilet plunger, which is designed to seal into the outlet of the pan, with enough water in the bowl to cover the cup.
- Push down gently first to expel the air, then plunge firmly several times and let the water settle.
- Flush once to test. If the bowl still fills and drains slowly, stop and call an engineer.
Keep a flanged plunger in each washroom block, separate from general cleaning equipment, so it is there when needed.
What Not to Do in a Commercial Washroom
Some habits that are fine at home create risks in a workplace washroom.
Avoid chemical drain unblockers. Under the COSHH Regulations 2002, employers must assess the risks from hazardous substances, and HSE’s guidance lists drain-cleaning products among them. HSE also warns that mixing bleach-based products with acidic toilet cleaners or ammonia gives off harmful gases, which is a real risk in a washroom where toilet cleaner is already in use.
Don’t keep flushing a slow toilet to “push it through”. Each flush adds water faster than it can drain, which is how most cubicle floods start.
Don’t let untrained staff use drain rods or toilet augers. They can scratch the pan or damage the trap, and a problem further down the system can’t be reached from the toilet anyway.
When to Call a Commercial Drainage Engineer
Call an engineer when:
- plunging hasn’t cleared a slow draining toilet
- the same toilet keeps blocking, even after it has been cleared
- several toilets, urinals or showers are slow at the same time
- there is a sewage smell in the washroom that cleaning doesn’t remove
- water or waste comes up through floor gullies or shower trays
An engineer can find where the blockage is and clear it properly. Drain jetting clears build-up along the length of the pipe, and a CCTV drain survey shows whether a repeat problem is caused by build-up, damage or a poor pipe layout. If a washroom floods or several toilets back up during opening hours, our emergency drainage team can attend.
Preventing Slow Draining Toilets in Gyms and Coworking Spaces
Most slow draining toilets in shared washrooms can be prevented by controlling what goes into them.
Provide a sanitary bin in every cubicle, not only in some, so users always have somewhere else to put wipes and sanitary products. Add clear signage asking users not to flush wipes, paper towels or sanitary products. Thames Water’s “Bin it, don’t block it” campaign has materials you can use. Where you can, use toilet paper dispensers that release a sheet at a time rather than large rolls.
Ask cleaners to report slow toilets as soon as they notice them, rather than waiting for a full blockage. Employers also have a legal duty here: the Workplace (Health, Safety and Welfare) Regulations 1992 require suitable and sufficient toilets at readily accessible places, kept in a clean and orderly condition.
For busy sites, a drainage maintenance contract puts washroom pipework on a planned inspection and cleaning schedule, alongside the shower drains covered in our guide to blocked shower drains in gyms and coworking spaces. Our guide to planned preventive drainage maintenance explains how this works.
Washroom Drainage Support across London and the Home Counties
London Drainage Services has worked with commercial clients for over 20 years, across London, Watford, St Albans and the wider Hertfordshire area.
If a slow draining toilet keeps coming back on your site, or you’d like to put your washrooms on a maintenance schedule, get in touch with our team.
Frequently Asked Questions
Why does toilet water rise then slowly drain?
It usually means a partial blockage. Water can still get past the obstruction, but slowly. If only one toilet is affected, the blockage is likely close to that toilet; if several are affected, it’s probably in shared pipework.
Can our cleaners use chemical unblockers on toilets?
We advise against it. Drain cleaners are hazardous substances under COSHH, some react dangerously with other toilet cleaners, and they rarely clear wipes or sanitary products. A flanged plunger is safer for a single toilet, with an engineer called if that doesn’t work.
Why are several toilets draining slowly at once?
Toilets in a washroom usually share a branch pipe or soil stack. A blockage in that shared section slows every toilet connected to it, so it needs clearing by an engineer rather than plunging each toilet.
How do we stop members flushing wipes?
Put a sanitary bin in every cubicle and add clear signage about what can be flushed. Some sites also ask cleaners to note which washrooms block most often, so signage and bins can be targeted there.
How quickly can a blocked washroom be cleared?
It depends on where the blockage is. A blockage close to the toilet can often be cleared in a single visit, while a blockage in shared pipework may need jetting and a CCTV survey to find the cause.
Should washroom toilets be on a maintenance contract?
For busy gyms and coworking spaces, planned maintenance helps catch build-up before it causes a blockage. It can cover washroom pipework, shower drains and external drains on one schedule.