Hot water spitting - pump or pipes issue

errlloyd · 26-03-2025 11:26AM #1

Hi guys,

I am wondering if anyone has any thoughts, because the pump guys told me to call the plumber, the plumber told me it was a pump problem, and I'd preferably like to avoid big call out fees if I can.

For the last six weeks or so, all of my hot water taps have all been spitting (quite violently) when first turned on (and then intermittently when left on). They would spit powerfully enough that it would a pretty significant amount of water all over the person standing in front of the sink and the whole room. Cold taps are completely unaffected.

At the same time the pump in the apartment has developed a very small leak. The pump is photographed, and the exact spot of the leak is circled. My three working theories are.

1: For some reason, the pump is pumping hot water to too high a pressure

2: There is air in the system from the leak?

3: The water is too hot.

I measured the water temperature with a food thermometer today, it is only 55c or so and it doesn't feel too hot - but the pump guys were fairly insistent that was probably the problem.

WhatsApp Image 2025-03-26 at 10.20.05_bf1b6c9e.jpg

10-10-20 · 26-03-2025 11:49AM

The first thing that I noticed on this setup was the way that the flex-hoses on the hot-side of this pump are twisted. I'd be replacing them with new hoses and see if that resolves the issues. as I feel that they could be closing over when heating up and that could be contributing to the issues. Anybody else?

Wearb · 26-03-2025 11:52AM

Perhaps download the installation manual for that pump. Those flexible connections might have to leave the pump in a vertical orientation.

That probably isn't the cause of your problem, but always start with the obvious.

errlloyd · 26-03-2025 11:56AM

Good tips - although I got this pump repaired before (about 2 years ago) by the ST reseller in Ireland, and that is the way he left it.

Hobby farmer · 26-03-2025 12:13PM

As above, those flexis on the pump are kinked and need changing. Could be the cause of your issue

T-Maxx · 26-03-2025 12:21PM

It has to be air in the system if you ask me. How or where it gets in is the question.

10-10-20 · 26-03-2025 02:41PM

https://www.boards.ie/discussion/comment/123299587#Comment_123299587

Cavitation on the pump due to the collapsed pipes could be drawing in air under pressure and then causing it to spit.

errlloyd · 26-03-2025 03:57PM

Thanks all, I took from your feedback that this was probably a pump set up problem and not a general plumbing problem. So I have a pump guy coming out.

I'll post the solution here so ya'll know and to help anyone in future!

errlloyd · 31-03-2025 11:47AM

Again, thanks for all the support. I got on to Domestic Pumps, and they had a guy out the next morning.

Al lof the rubber seals on the hot side of the pump were wrecked, and there was something wrong with the pressure cannister on top. He was here for a good while (about 2 hours) getting it all sorted. Before I moved in the hot water was set way too high and he reckons that was the cause of the problem. Sorted it all for the price they had quoted on the phone, despite it being a shopping list of issues. I was happy with that, and glad to get it sorted. He wasn't too worried about the flexi-hoses, though!

Thanks again, everyone.

10-10-20 · 31-03-2025 01:06PM

https://www.boards.ie/discussion/comment/123313375#Comment_123313375

Good feedback. Having the water temperature too high will cause an endless amount of issues alright as everything just fails much sooner.

Kaisr Sose · 31-03-2025 01:47PM

I got on to Domestic Pumps, and they had a guy out the next morning.

That was a good choice. I have used them a few times for rentals and they were great.

Agent plumber standard response is to advise a new pump even where it's just the PCB.

Hot water spitting - pump or pipes issue

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