Boosting Hot Water Pressure in New Home with Gravity Fed Sys

[jameshobiecat]

I am a couple of weeks away from moving into a new build house, on a recent visit to the property I was horrified to see that the developers had installed a gravity fed hot water system rather than a combi boiler. In fairness to them, they didn’t say it would be combi, I just assumed everything was these days.

I have accepted that I’m stuck with an inefficient system with limited hot water capacity but I’d like to improve the hot water pressure to allow for fitment of a modern tap in the kitchen (all the nice ones need 0.5bar plus), and a to have a half decent shower. It is only a small house with a single shower and I’m not after mega pressure, just something similar to a combi output will do. It is worth noting that the cold supply is mains pressure throughout, not gravity fed, so does not require boosting. The hot water cylinder is situated in an airing cupboard next to the master bedroom and there is space for a pump next to it.

As always, money is tight, so I’m looking for a cheap way to get a modest improvement. £500 would be absolute max.

As I understand it there are two options; a low pressure (approx 1bar) boost pump or to convert the hot water cylinder to being pressurised by the mains. Which is best? I do not know the make or spec of the hot water cylinder.

If I’m to go down the pump route, I see the Grundfos UPA 15 90 has had some negative comments on this forum but they seem to relate to its inability to supply large multi outlets systems. Would it be suitable for my application or is it just too weedy at an extra 0.5-0.75 bar? Can anyone recommend a (cheap) alternative? Is a low pressure pump such as this going to be too noisy? How much is it likely to cost fully installed?

If it’s the pressurised tank route, what is involved? How well does it work and what is it likely to cost? Are all tanks suitable or is it model dependent?

I’d be grateful for any help offered as I need to make a decision quickly, I have the developer breathing down my neck.

Regards, James

 

[bass]

if you only have 500 quid at your disposal i would say its a no brainer(Pump) regarding hot water and heating systems you do need to consider the incoming mains pressure which does have a big say. Combination boilers are used primarily to save money and are usually used taking into account the demand on the hot water outlets and heat calculations.These boilers require a minimum incoming mains pressure to work correctly.

 

[IKM]

I don't think a gravity fed hot water system is necessarily a bad thing. The boiler will be simpler and most likely more reliable than a combi and you will be able to have a full cylinder of hot water for multiple baths, showers etc. With a combi the flow rate of the mains pressure water has to throttled back to get a decent temperature rise.
I also have gravity fed hot water. I fitted a Triton AS2000 power shower which is connected to the gravity fed hot and cold water. The performance is excellent. The hot flow rate from our modern kitchen tap with ceramic disc valves is satisfactory. The cold water storage tank is in the loft about 5m (=0.5 Bar) above the kitchen tap.

 

[jameshobiecat]

Thanks for the advice.

The header tank in the loft which pressurises the hot cylinder would end up approx 4m above the kitchen tap giving 0.4bar. I think the tap requires 0.5bar min but it may be 1bar.

Has anyone any experience of the Grundfos UPA 15 90 in a modest application like this? What is the all in cost?

Given that i'd like to boost the whole house, do I need a surrey valve? Or is it a bad idea to boost the whole house? Do I need a pump with a small pressure accumulator?

James