Does my rat valve need maintenance? Can i not just fit & forget?

All manufacturers of rat valves will stipulate an inspection/maintenance interval following fitment.

Typically this involves a cost so people often ask us whether this is just a prudent measure or an actual necessity?

Think of the life a rat valve leads… it’s subject to a continual onslaught of differing water levels, rates of flow, pH levels, water temperatures, all manner of solids, emulsified fats & greases, limescale and plant roots.

And it has to suffer this alone in the pitch black of a manhole too.

Aside from mental toughness, it needs moving parts to accommodate these challenges and its these moving parts that are susceptible to becoming less free moving as time passes.

A loss of movement in something that you rely on to pass your waste water is a worrying thought and so we always say that it’s a logical decision to have a maintenance programme for your valves.

A proactive strategy is likely to be a better idea for something controlling the flow of waste rather than just waiting for a problem to occur and then dealing with it reactively.

Whether this is done quarterly or annually depends on the type of valve and the type of location but essentially these are the key things that work to shorten valve life and generally cause problems.

The more of these factors you have in your waste water system then the more frequent your valves should be inspected & maintained.

1. Interceptor Traps

These frequently block causing water to rise and fall through the rodding eye cap (assuming the cap is not in place).

This changes the rate of fall for the drainage system behind and typically results in slower flow rates plus standing water on the approach to the interceptor trap.

Slow flows and standing water don’t push solids cleanly through valves and reduce the effect gravity has on the flaps.

End result is generally a clogged valve and rats passing back through.


2. Surface Gulleys with Missing Grates

Twigs, small plastic bags, clothes pegs and other foreign matter that exists above ground drops into the open gully and risks being washed down to the valve with the associated risk of entrapment/snagging.

3. Fats & Greases

Stainless steel valves provide a nice cold lump of metal for emulsified fats and greases to congeal out on.

Big problem for restaurants or anyone who disposes a lot of cooking oil down the kitchen sink.

4. Kitchen Roll & Wet Wipes

These don’t immediately break down in water unlike toilet paper and so are very good at wrapping themselves around valve assemblies and then gradually congealing down into a solid encrusted mush.

It includes the centre-feed roll species of paper as well as all forms of sanitary waste and latex contraceptives.

Ear buds too aren’t good.

5. Limescale

Present in all foul water systems, this white crusty material will gradually encase a valve just like it encrusts the insides of pipes.

6. Heavy Sediment Levels

More of an issue on the combined waste systems of older buildings, sediment contains tiny particles of grit that can get wedged in hinge mechanisms accelerating wear or reducing tolerances.

7. Tree Roots

Valves are always inserted within inspection chambers and often very fine tree and plant roots will find their way in through the chamber walls to wrap around the valve and slowly choke it.

8. Cement Slurries & Paint Residues

Surprisingly these are common introductions into waste water systems and both are essentially adhesives that will dry out around your valve to leave troublesome residues that will adversely affect the valves operation.

9. Changing Pipe Diameters & Valve Positioning

The internal dimensions of pipes will reduce over time due to limescale or grease deposits in the same way human arteries clog and so it’s important to frequently check the valve flap alignment is optimal.

The valve itself is also likely to move slightly over time as ultimately they all rely on friction alone to stay in place.

If the tip of the flap starts to touch the floor of the pipe then you are asking for trouble!

So what maintenance is required to keep all this at bay?

Well choose a good valve to start with – the difference in design and materials between the top of the range valve and the lower end of the market is huge.

Fit the best and you’ll massively reduce the likelihood of subsequent issues.

Then choose a trained installer – fitting valves is surprisingly difficult and something just hammered in with brute force via a long arm and with no CCTV check off is a prime candidate for a long saga of issues.

Once top quality valves have been installed by trained installers, all they need going forward is a little daylight now and then so they can be given a hot bath, a good clean and brighten and some well-earned lubrication of any moving parts.

Once the valve is removed it should be fully descaled and degreased, cleaned to restore all surfaces to a nice smooth substrate and the hinge points protected with some water-dispersal lubricant.

It should then be reinstated by a trained installer who can ensure the flap angle is correct, full range of motion is possible and check off its positioning with a CCTV camera.

If you do this at the right frequency for your particular installation then you and your valves will have a very long and happy relationship – plus a rat free life!

Pestology offers a full valve maintenance programme and can advise on inspection frequency for your particular application – all our engineers are trained valve installers and conduct a CCTV check-off.

Please get in touch to discuss.


Nordisk valves are the very best ‘rat blockers’ available and have a proven history of providing reliable waste flow as well as being 100% rat proof when operating efficiently.