The water pressure is very strong in Tallaght at the moment. But it has nothing to do with the pipes. There are allegations of lies on the doorsteps and dirty tricks across social media. The Socialists are accusing Sinn Féin of being soft on the national question, which for them boils down to water.

Sinn Féin say the Socialists are trying to muddy it. Meanwhile, with a massive water fight raging between the two frontrunners, the rest of the candidates in Dublin South West are in danger of drowning in what seems increasingly like a single-issue byelection.

Cathal King is standing for Sinn Féin. A councillor in the Tallaght area for over a decade and a former mayor of South Dublin, he lists his occupation as "a full-time public representative". At the rate the party employs candidates and prospective candidates, Sinn Féin might soon have to apply for membership of Ibec.

The consensus, bookies included, is that King should comfortably take the Dáil seat vacated by Fine Gael's Brian Hayes when the votes are counted this Saturday. Paul Murphy – a former MEP and a Joe Higgins protégé – is hoping to pull off an upset and sneak a victory for the Anti-Austerity Alliance. Clearly, Murphy sees just one opponent in his way – Sinn Fein, and he wants to exploit what he believes is the party's weaker stance on water charges.

That doesn’t look to be the case in the Tallaght area, where it’s hard to miss Cathal King’s face on huge “Stop the Water Charges” posters placed at strategic points around the constituency. But until the byelection campaign gathered a head of steam and Murphy appeared to be gaining in the polls, Sinn Féin had been somewhat, well, watery, on the question of whether or not the scrapping of the charges would be a deal-breaker on going into government.

Not a red line issue

Their finance spokesman said in early September that axing them would not be “a red line issue”. Now, it most definitely is, with King going as far as to say he will not be paying for his water. What changed? Muphy’s team produce a poll which they say was taken in the constituency by one of the bigger parties. The results, if they are accurate, will have put the wind up Sinn Féin on the run-in to polling day.

Taken two weeks ago, it has Cathal King on 25 per cent with Paul Murphy coming in at 21 per cent, Fianna Fáil at 17 per cent, Fine Gael and a former Fine Gael independent candidate hitting 12 per cent and 10 per cent respectively, Labour at 7 per cent and others at 8 per cent.

“The momentum for us is growing” says Joe Higgins, who was canvassing for Murphy outside the Square Shopping Centre yesterday. “I was knocking doors in Greenhills last week and I thought I was canvassing in Blanchardstown.”

On the final weekend of the byelection, candidates and their teams were out in force. But Sinn Féin was conspicuous by its absence. This wasn’t because of the unusual row that blew up on Saturday between the two main rivals. Murphy accused the party of being behind a fake posting on Facebook purporting to show him spreading falsehoods about Sinn Féin’s policy on water charges. The page was shared by a number of the party’s politicians, including Mary Lou McDonald, who immediately and graciously apologised when she discovered the contents of the page were untrue.

While Murphy accepted the apology, one sensed his team still suspect the fake page was a “panic” reaction from a Sinn Féin supporter.

Fine Gael’s Cait Keane is also in the shopping centre. She is more interested in spreading the message of “jobs, stability and growth”. One of her workers tell us that water is not coming up on the doorsteps as much as the frontrunners might want people to think.

“We were at a community debate last week, and all they wanted to talk about was how committed they were to getting rid of the charges. People were falling over each other to say how they had been arrested over the water and some were even arguing over who got arrested first.”

Meanwhile, all election squads – bar Sinn Féin – mobilised to do the churches. Former Fine Gael member, now running as an Independent, Ronan McMahon hands out pens outside St Dominic’s Church. His leaflets caused some confusion, as he styled himself “Independent Fine Gael” but he appears as “non-party” on the ballot paper.

The businessman, who is the son of Larry McMahon, who was a FG TD back in the seventies, says unemployment is the big issue for him. He had four teams out yesterday, and outside St Dominic's he had the considerable presence of Lucinda Creighton lending her support. Feargal Quinn turned out for him on Saturday.

Creighton support

Lucinda says she supports McMahon because he is independent-minded and “a man of principle”. She’s in great demand. “I’d like to see you as the first female taoiseach,” says one man. “You have great uumph” says an elderly woman, wondering if she might ever return to Fine Gael. “No, I’m very disillusioned, I’m afraid,” she replies.

Back at the Square, Paul and Joe are mopping up a lot of signatures for their anti-water charges petition. They say action and opposition is needed now, not some time in the future when Sinn Féin might be in government "and who knows what they might do then?" The Government has to be sent a strong message on Friday, Joe tells passersby. "It would be a sickener for Enda Kenny if Paul wins." It'll all be water under the bridge by Saturday.