Aquabox System Faulty

CR 7

I moved into a new build house with an Aquabox setup, and have been having ongoing issues with the pumped cold water side. The system does not appear to be able to hold pressure, pump starts immediately on opening the cold taps even a dribble. There's water hammer most of the time on pump starts for cold only. The hot side seems to be working fine, after opening the taps the water flows for a few seconds until the pressure drops and the pump engages, which is what I'd expect.

The aquabox suppliers were out and said the cold system shouldn't be working like that, mentioned it may be an expansion tank issue. They also changed the controller on the aquabox and changed some settings to try and improve it, but no difference. They only supplied the unit itself so aren't responsible for the rest of the plumbing for it.

I've brought the plumbers back out to try and get them to troubleshoot, but they just say it's meant to be like that. There are 2 expansion tanks in the system and they told me one day that one is for hot and one for cold. The next day, they said that one is for heating only, one is for hot/cold taps. They checked the pre charge pressures in both and apparently those are correct. They're almost finished on site snagging so have no interest in fixing anything, so trying to fob me off.

Is it a case of getting another plumber out to diagnose the issue? Or does anyone have any other tips to test out?

Lenar3556

If it is a new build house, from a legal perspective I would push hard on the builder to bring this to a satisfactory conclusion, whatever that may be. It will probably be relatively easy to resolve, but strike now while the iron is hot.

What precisely are the issues? You mention that the system doesn’t appear to be able to hold pressure, but I am not sure why you suggest this?

From your description, I wonder is the expansion vessel fitted on the hot side of a pressure reducing valve (likely fitted to the incoming feed to your hot water cylinder), and hence no expansion on the cold side?

This would concur with your description of a slight lag in pump start when you have a hot water demand, but no lag on cold, together with water hammer on cold. If this is the case, a second expansion vessel fitted immediately downstream from the pump output may be helpful.

CR 7

https://www.boards.ie/discussion/comment/122768045#Comment_122768045

The water hammer really is the most concerning issue. The pump starting immediately on opening the cold taps is annoying but shouldn't really cause any issues in itself. The aquabox supplier confirmed that the system should be set up so that for both hot and cold when you open the taps water should flow for a couple of seconds with pressure visibly reducing until the point the pump starts. This is how the hot system works, but the cold starts the pump almost immediately when the tap is opened even slightly. The water hammer also indicates to me that the change in pressure with the pump on is too sudden.

As far as I can see, that's how the expansion tanks are set up. The plumbers gave two contradictory explanations of how they are set up, and the labelling of pipes is quite poor/non-existant.

If it is the case that there's no expansion tank on the cold system, I was also thinking that there should be one added, so thanks for agreeing with that at least. Time to try and get them to actually sort it out this time so.