Plumber double dipped on work that kitchen installers said they’d cover

I’ve been having my kitchen renovated and had to use our strata plumber for part of the job as that’s something our body corp has agreed on – we have a hugely expensive hot water system so use the strata plumber to turn it on and off before other plumbers like the kitchen reno ones can do any work. I asked the strata plumber to put in isolation valves at the same time.

I showed them the plans for the new kitchen – they said they do a lot of renovation work for big companies – sink moving to a different wall, pipes extended, washing machine going where old sink was, etc. They put in the isolation valves where they would go if no changes were occurring to the kitchen, so that the washing machine would block access to the valves. They say they checked with the kitchen company plumbers via the phone but those plumbers disagree and when they arrived said that the valves were in an impossible place and had to be moved.

As the kitchen company plumbers weren’t available the next day, and as the strata plumbers would have to come out again to turn off the water as the valves were being moved, the two lots of plumbers arranged among themselves for the strata plumbers to do the whole job – moving pipes, etc. The kitchen company project manager was party to this discussion and told me over the phone, “No problem. We’ll cover it.”

I then received a bill from the strata plumbers for the lot – an amazingly expensive bill – they’d sent two plumbers on the first day although I know that two other units in my little building had their isolation valves done by them and both times only one plumber did the work. My strong impression was that the boss was training the younger plumber in this specific work and that was why he was there.  But he was charged for.

How much – if any – of this can I fight and how? The kitchen company project manager now denies that he said the company would cover any of it. I’m at a loss to know how they were going to give me a kitchen with no water to the sink, dishwasher or washing machine. I believe the project has gone over budget because the designer quit the company as he was working on my plans, and according to the kitchen company’s plumber when he saw the kitchen for the first time, “The designer really dropped the ball.” It seems he hadn’t drawn in or costed for some electrical and plumbing work when he drew up the plans and contract.  Water was to appear by magic.

So I’m accepting that I’ll have to pay at least part of the bill for the work that the strata plumbers did on the second day but I’d like to challenge the work that they did (charging for two plumbers) on the first day, which all had to be redone as it was in the wrong place. The head strata plumber, whose company it is, claims that it would have been possible to get a hand in and access the isolation valves but given that the washing machine completely fills the space, I can’t see how.

Can you please tell me how much – if any – of this can I fight and how?