--- title: Pontygwaith: AdBlue in a Diesel Tank, Explained canonical: https://www.petrolinadieselcar.co.uk/adblue-in-diesel/pontygwaith-rhondda-cynon-taf/ location: Pontygwaith county: Rhondda Cynon Taf latitude: 51.638150 longitude: -3.432110 service: AdBlue in a Diesel Tank updated: 2026-10-18 --- # How It Occurs and How to Avoid It: AdBlue in a Diesel Tank in Pontygwaith If AdBlue is already in your diesel tank, stop reading for a moment: leave your engine and your ignition off and phone 0333 366 0103. Around Pontygwaith, catching it before the engine runs usually means draining and a full flush where it stands. If you're reading before it has happened, the remainder of this page is about why it happens and how to make sure it does not. ## Two fillers, two tanks: AdBlue in a diesel vehicle Plenty of modern diesels on the roads round Pontygwaith and Tylorstown carry two liquids, not one. Diesel goes to the motor. Kept in a tank of its own, AdBlue is sprayed into your exhaust stream to clean it. Different tanks, different fillers. Many of motors have a single flap for the two, while some move the AdBlue filler to your boot or under the bonnet. Topping up your diesel side at the pump goes on all the time. A driver who has to stop and work out where it goes normally fills the AdBlue side, from a bottle, and much less regularly. It's in that gap that the slip happens. ## Pontygwaith: how AdBlue in the diesel tank occurs Three things tend to come together, and carelessness is rarely one of them. On a drive off Llewellyn Street before work, or in the car park outside the pub in the village heading home: that is where the rushed top-up happens. Why the rush? As AdBlue gets low the car tells you, and if it's gone, limp mode follows. The old car's cap is where the hand goes — but a hire car, a new motor or a company car puts the fillers elsewhere. That is a second thing: a new car. No part stops the pour once it has started, since a bottle with a spout goes into a diesel filler as easily as an AdBlue one. The bottle fits. Whether it happens in Stanleytown or the middle of Pontygwaith, it's the same few seconds. ## The AdBlue filler and the diesel filler: telling them apart Whether a Pontygwaith forecourt or a drive out in Llwynypia, spend a couple of seconds over these before any is poured in. - Position misleads; the cap doesn't. AdBlue ones tend to be blue or carry the name "AdBlue" — diesel caps usually do not. - On many motors, size gives it away: AdBlue gets the smaller filler neck. - A label inside your fuel flap frequently says which fuel goes where, on plenty of cars. Check for it. - The handbook. If the filler isn't by your diesel cap, it is in the boot or under the bonnet, and the handbook says which. - Collecting a hire or company car, perhaps at the car park outside Llwynypia? Ask the person who drove the car last before you set off, rather than once the light goes on. ## Topping up AdBlue without it reaching your diesel tank Wherever in Rhondda Cynon Taf the light comes on, here is a routine for that day. - Pull in on level, engine off, with time to spare — not hurried on the side of School Street. - Say "AdBlue" out loud as you unscrew the cap, once finding the AdBlue filler and read it. Silly, perhaps, yet it works. - Leave the diesel cap on. If both sit under one flap, check your diesel cap is still closed before you lift the bottle. - Using the bottle's own spout, tip slowly — and stop when it is full or the bottle is empty. - Close the cap, then check again — making sure the diesel cap remained shut the whole time. Only then, start the car. Find during the second or third stage that AdBlue went into the wrong filler? That is where you stop. Do not go on to stage five. ## Pontygwaith: already put AdBlue in your diesel tank? Then the order of things is short. Do not start your motor. Keep your ignition off as well, because on many diesels switching it on by itself runs your fuel pump. Topping up with diesel won't dilute it: rather than mixing, AdBlue sinks to the base of the tank, just where fuel is drawn from. Ask the staff to help roll your car clear of the pump if you are at a forecourt — the Shell, the Asda or anywhere else. At home in Pontygwaith? So the vehicle remains where it is. Where the motor has been run already, stop safely then turn the car off. On the M4, under 10 miles from Pontygwaith, that means the next exit. Tell us about how far it went: a run towards Cardiff, under 25 miles away, is a bigger job than a short hop across Pontygwaith. ## Our arrival in Pontygwaith, and what occurs next Our engineers come to the car wherever it has stopped, whether that's outside the local primary school, near St Mary Magdalene Church or on your own driveway. Both the work and our price depend on three answers — what liquid, which amount, and whether it has run — so our technicians ask. On the call itself, you are told the price — ahead of anything else. Then your tank is cleared and the fuel system rinsed thoroughly. Much more than with petrol, it matters with AdBlue: the crystals build up, certain metals are attacked, and none of it clears out on its own, however long it is left. Once the fuel filter has been flushed — or renewed, where needed — fresh diesel is added, and then the car gets tested. The motor is started next and checked to be sure it runs smoothly, all before our technicians go. With pumps fine on a working forecourt and quiet enough for use outside a house at night, most jobs in which the motor has not run need roughly half an hour after our engineers arrive. You pay on the day, with nothing upfront, and get a VAT invoice and an engineer report for your insurer. Plenty of insurance policies include misfuelling cover, and so it is worth checking yours whilst we're on the way. ## About Pontygwaith Pontygwaith is a village in Rhondda Cynon Taf, situated on the banks of a river at an elevation of 156 metres. Pontygwaith lies near the communities of Stanleytown, Penrhys, and Wattstown, and is approximately 15 miles north of Cardiff. Pontygwaith has a population of around 1697 people, predominantly living in terraced housing. Pontygwaith is located in a region of south Wales, within commuting distance of major cities. ## Pontygwaith and Rhondda Cynon Taf: AdBlue drains across the area Throughout CF postcodes, our teams that cover Pontygwaith — a village — work the surrounding spots too, Wattstown and Penrhys among them. A postcode starting CF43 3 gets the van to you fastest. Moving the car is not needed. Wherever it sits — near Saint Mary, in a layby heading to Graig Steet Park, on a drive — that is where it gets cleared. Assuming won't help at the back of Millennium Flame, on a border, or somewhere hard to describe; ring and ask. ## Pontygwaith people: the short version Always, the cap; after that, the tip. Petrol in Diesel empties it where it stands, anywhere around Rhondda Cynon Taf, if AdBlue has gone in your diesel tank anyway — so leave the car off and call 0333 366 0103.