Keeping the Mount Hot Pools hot is a juggling act – balancing technical constraints against the requirements of the pools' complex resource consent, says Tauranga City Aquatics Ltd CEO Tania Delahunty.

The hot pools are back in action this weekend after a recurring electrical fault took the pools out for a second time last weekend.

The first closure on Friday was caused by an electrical fault.

The pools reopened on Saturday but another fault occurred later that night, causing a second closure on Sunday.

The closures cost about $7000 in lost revenue.

'It was the electrics to the bore pump, it was unexpected,” says Tania.

'Water got into an aspect of the electrics, so they had to pull it up and have a look at it. It's burned some things out I understand. It's all repaired and back up and running, but it was something that was unforeseen.”

Even without breakdowns, keeping the hot pools hot requires balancing the amount of water drawn from the bore, with the amount and the temperature of the permitted discharge into the harbour.

Add the fact the facility is part new, and part old, and the two do not always mix.

Hot salt water is pumped up from the bore and run through heat exchangers which heat up salt water pumped from Pilot Bay. This is chlorinated and used to fill the pools.

Keeping the pools hot in summer is easy but whether they can keep them hot in winter without breaking the resource consents is another issue, says Tania.

'We are looking at other aspects of how you manage the hot water, bearing in mind anything we do down there impacts the resource consent.

'So if we heat the water up for example, if we got more hot water, which would be great, I would have to discharge it at a required temperature still.

'Even if I have more hot water in the pools if I can't cool it somehow, then discharge it, I breach my resource consent.”

The resource consent governs how much hot water the pools can draw from the ground, how much can be discharged into Pilot Bay and how hot it is when it is discharged into the harbour.

Ecological reports on the effects of the discharge are part of the resource consent.

'That's what we have to manage,” says Tania. 'We looked at a cooling tower as part of the redevelopment, but a cooling tower is tall and we would breach the height restrictions which is what caught us with the redevelopment.

'I can't put in a cooling pond because I would take up green space which would impact my consent, which I can't do because that was part of the redevelopment.”

The only cooling mechanism signed off by DOC, The Historic Places Trust, and iwi was under floor heating that was to be part of the redeveloped building.

The hot water from the pools would be run under the concrete floor, heating the changing rooms, while lowering the temperature of the discharge water which would then be poured into Pilot Bay at the correct temperature.

'And we can't do that now because we are not rebuilding, and you can't retro-fit it because it gets poured in when you pour the concrete floor.

'It's a massive catch 22. Historically I could draw more water out of the bore to make it hotter, then historically I would breach my consent by the amount drawn out and breach the consent regarding the discharge.

'It's a fine balance between heating the pool and meeting all the obligations.”

The Mount Hot Pools' hot salt water core temperature is about 45-46 degrees Celsius at the moment. Pool temperatures are supposed to be 38-39 degrees Celsius.

The bore water temperature at Memorial Park is 51 degrees Celsius and the pool is heated to 28-29 degrees Celsius.

'We can easily get that temperature,” says Tania. 'If you are looking at the hot pools we are trying to get 38-39 degrees out of water, that's only 45-46 – and that's really hard work.

'It's got to go through all the pipes, all the heat exchangers and the efficiencies in anything is never that good. You are only able to lose a few degrees through all that whole process.

'And then if you add in cold air in winter it just makes it really hard, and it's not so easy to just throw in some more hot water because we get caught at the other end. If we could draw as much as we wanted and discharge as much as we wanted, it would be easy.”

The hot pools are also operating in an incredibly corrosive environment.

'People fail to understand chlorine is highly corrosive, salt water itself is corrosive, and hot salt water is incredibly corrosive.

'We've got all three sitting together, mixing up and it makes an incredibly corrosive environment.

'How we treat chlorine in hot pools is completely different to how we treat it in the other pools because it reacts completely differently in the salt water.”