Constantly losing hot water pressure from Direct Vented Cylinder

[Hambone]

Hi, I have a hot water cylinder which feeds 3 outlets (kitchen sink, basin in bathroom & bathtap) which has never had very good pressure (probably because of the set-up) but last year got so feeble that a guy suggested fitting a pump alongside the cylinder. This can work fine but then all of a sudden can lead to a complete cessation of hot water, he has got it working again before but it stopped the other day and he wasn't available to resolve so another really useful guy came and sorted it with a hoover in no time but said it could be the pump drawing off the hot quicker than the header tank could refill the cylinder (and we ought to have a flange on the top of the cylinder as well-even though it doesn't supply hot to a shower) and, as he predicted, we are back to it being stop/start.

I've put some photos on that show the set-up, (which is identical to other flat owners, although their pressure was never as bad as mine before the pump was fitted), I was wondering if there is something inherently wrong with the set-up (I think the builder of the flats used a cylinder which could also be used as indirect but it has always been immersion only) and whether having the pump is causing these airlocks ?. We were thinking we might be able to install a header tank with more capacity although tbh I'd rather just not have the pump and I'd be happy with just reasonable hot water pressure.

Hope the experts might be able to offer some guidance, I'm considerably better at sawing things ! cheers

 

[fowlerboi]

The cistern is tiny. That pump can pull up to 32L/min while your cistern looks like its only holding 45L. If you're running the hot taps for more than a few mins I expect you're depelting the cistern which then sucks in air. This would also tally up with your plumber solving the issue with a hoover

What is your flat setup? kitchen taps/basin taps/ bath taps?/shower

 

[ShaunCorbs]

😀 wrong black tank needs to be 50 gallons for a pump yours is maybe 2 gallons

 

[Hambone]

The cistern is tiny. That pump can pull up to 32L/min while your cistern looks like its only holding 45L. If you're running the hot taps for more than a few mins I expect you're depelting the cistern which then sucks in air. This would also tally up with your plumber solving the issue with a hoover

What is your flat setup? kitchen taps/basin taps/ bath taps?/shower

Thanks for the comments, appreciated, set-up is all of the above except the shower I have installed is an electric one, so fed off the cold, cheers

 

[Hambone]

😀 wrong black tank needs to be 50 gallons for a pump yours is maybe 2 gallons

Cheers for the comments, appreciated, sounds like the pump has turned a poor hot water pressure situation into an on/off hot water situation, cheers

 

[ShaunCorbs]

Tbh your best bet is to change the cylinder for an unvented

 

[fowlerboi]

What I mean is what taps do you have in each room?

Just this week I've had to change a load of taps on a fortic system similar to yours and haven't had any issues with flow rates if the right stuff is selected

 

[Hambone]

Tbh your best bet is to change the cylinder for an unvented

Thanks, certainly something to consider, I'm on my own so really only need basin, kitchen sink and the odd bath (have an electric shower) so pressure doesn't have to be super but pre-pump it got really feeble and I initially thought could it be limescale in the top of the cylinder or something, cheers

 

[Hambone]

What I mean is what taps do you have in each room?

Just this week I've had to change a load of taps on a fortic system similar to yours and haven't had any issues with flow rates if the right stuff is selected

Sorry, mixer in the kitchen, regular (separate) hot & cold on the basin & bath, cheers

 

[ShaunCorbs]

Thanks, certainly something to consider, I'm on my own so really only need basin, kitchen sink and the odd bath (have an electric shower) so pressure doesn't have to be super but pre-pump it got really feeble and I initially thought could it be limescale in the top of the cylinder or something, cheers

Pressure won’t be the best less than 0.1 bar as the tank isn’t that high ideally you would want it 3m above the cylinder

 

[fowlerboi]

Which taps are causing the issue? Seperate bath basin taps should be fine as long as the pipework has been done right. The kitchen tap is the tricky one but its certainly possible to still get a good enough flow rate out of it.

 

[Hambone]

Pressure won’t be the best less than 0.1 bar as the tank isn’t that high ideally you would want it 3m above the cylinder

Yeah, not the best is it, I have a couple of mates in the block & there's was never as bad as mine, must be something specific to me I guess

 

[Hambone]

Which taps are causing the issue? Seperate bath basin taps should be fine as long as the pipework has been done right. The kitchen tap is the tricky one but its certainly possible to still get a good enough flow rate out of it.

My plumber (new guy) is going to strip out the pump tomorrow and restore the status quo, will re-assess after that & hope it doesn't stop completely !, thanks for the guidance

 

[ShaunCorbs]

Yeah, not the best is it, I have a couple of mates in the block & there's was never as bad as mine, must be something specific to me I guess

How old are your taps ?

 

[Hambone]

How old are your taps ?

The basin & bathtaps will be pretty old to be fair, the bath ones could be as old as the initial installation i.e., 30 years