Heatslave 15/19 - Low hot water pressure.

[Doris LC4]

Dear experts,
I moved into a house in 2020 with a private water supply and a Heatslave 15/19 oil fired boiler. Water pressure wasn’t an issue initially as we had a pump in the line to increase pressure as the previous owner enjoyed a power shower. The pump then failed and wasn’t replaced and I bypassed the pump with pressure then being decent for both cold and on demand hot water from the boiler.

However, over the past 4 years the hot water pressure at the tap has gradually decreased to the point where it barely kicks on at the bathroom basin. As water treatment goes I have 2 cartridge filters and an UV unit. Pressure increases slightly when I change filters.

My gut feeling is that something is clogging / furring up over time and that its inside the boiler. My oil boiler guy isn’t shining much light on the matter. Are there any experts out there that know the Heatslave boilers well as to what could be blocked / clogged / furring up within the boiler to reduce pressure at the hot water at the tap?

For info I I have decent enough cold water pressure at the tap which makes me think its the boiler causing the problem and the water pressure gauge in the boiler is giving me 1.2 bar max for the central heating side which works without issue.

Thanks everyone

Euron

 

[oilhead]

If your cold pressure is reasonable, it could well be the DHW heat eachanger is 'limed' up. Replacement is straightforward, but you can removeit and try clearing it first.

 

[Doris LC4]

Thanks oilhead. I’ve just downloaded and read through the installation and maintenance manual for the Heatslave 15/19. I note one the expanded view of the flow switch assembly that there in a little inlet filter that sits in the cold inlet line prior to the flow switch.
Having looked them up, it seems a very fine plastic mesh filter. Given that I am on a private water supply from a stream with 2 particle filters in the shed, it is not impossible for some crap to make it through over the years.

I also see there is a flow regulator which sits in the cold water feed line on the boiler side of the flow switch, could this also become clogged again given I’m on a private water supply?

Could my problem be down to this flow regulator / inlet filter being clogged?? I don’t think my plumber has changed either in the 5 years I’ve been here and I seriously doubt the previous owner would have replaced it!

What are your thoughts?

Thanks.

 

[oilhead]

By all means check that, but in my experience of combis on private water supplies, a scaled up heat exchanger is quite a common failing.
Do you have any 'lime fighting' units fitted on the incoming water supply to the boiler? Do your taps show any evidence of calcium deposits on the outlets?

 

[Exedon]

We look after a number of oil combi's on borehole/private supply's.
As above I would suspect plate to plate heat exchanger.
All the one's we look after have now got water softeners on .

 

[Doris LC4]

Thanks for the responses guys. Here in North Wales we live in a very soft water area and never have any limescale on kettles or taps. Our water pH is slightly lower than it should be though. Could this be a factor in fouling up the heat exchanger plates??

Thanks.

 

[Doris LC4]

An update for you experts. Took off the inlet pipe today and the gauze inlet filet was mega clogged with crap from the private water supply as was the 15 l/min flow regulator insert on the boiler side of the flow switch, I’ve cleaned both these bits and put everything back together. Ever so slight increase in hot water pressure at the tap but not as I’d expected.
I therefore bow to your expert knowledge guys and will look to get the plate heat exchanger replaced. Having seen the inside of one of these on a YouTube vid this afternoon, the channels are quite narrow and guaranteed my nice lower pH water supply has eaten it up over 20 years!

I’ll update one I’ve had this done.

Cheers.