Boiler / Hot Water Pressure advice needed

Jeepers_Creepers

Fair do's  - that orange one is 10 times as big. :-)

DettaWalker

Jeepers_Creepers said:

They combine cold water storage along with a pump.

I think they operate in one of two ways; most (Grundfos, Salamander, Pump World etc) fill their tanks normally with mains water, and will then pump it on demand to the house's supply. Others - Challis comes to mind - works differently by pumping the mains water at the required max rate of 12lpm into a pressurised accumulator (which has an expansion vessel inside it). This then stores the water under pressure, so it's released to the house under this 'unpumped' pressure.

The only one I have any experience of is the Grundfos*, and this was used in a 6-storey flat where water trickled out the kitchen tap. With the Grundos, the flat owner reported showers to be almost 'painful', and he actually had a pressure reducing valve fitted to its outlet to calm the 4+ bar pressure!

I personally prefer the 'idea' of the Challis where the tank is pressurised in advance, so the water is then released in a more natural way without a pump firing up every time to drive it like with the Grundfos.

For either, the very best solution would be to fit it outside the home, in the garage or perhaps a purpose-built insulated 'shed'.

* https://www.anchorpumps.com/grundfos-4-5-bar-home-booster-240v

https://www.challisshowers.com/about-the-company

https://www.pumpworld.co.uk/Our-Products/ProdDetail/catid/23/eid/45240/smart-rectangular-fixed

Thank you - will do some more research today on the links you've provided. I've tested my flow rate on the outside tap and it is roughly 20l/minute. So my flow rate may be adequate for an unvented cylinder after all. I just don't understand how I lose so much flow rate between the outside tap and the kitchen tap when they are roughly 5 metres apart. But maybe it has something to do with the construction of the kitchen tap. 

Jeepers_Creepers

DettaWalker said:

Thank you - will do some more research today on the links you've provided. I've tested my flow rate on the outside tap and it is roughly 20l/minute. So my flow rate may be adequate for an unvented cylinder after all. I just don't understand how I lose so much flow rate between the outside tap and the kitchen tap when they are roughly 5 metres apart. But maybe it has something to do with the construction of the kitchen tap. 

Quite possibly - kitchen taps are often 'eco' and have flow restrictors built in.

When you get 'G3' installers in to quote, they will test this properly. Make sure you have a copy of their results...

If you are in any doubt whether unvented will work well, I'd factor in the possibility of having to add a mains booster in your garage or similar. (They do not recommend having them fitted in lofts in case they leak, but the chances are probably no worse than for cylinders and boilers. There's also the extra weight, of course, but that can usually be catered for, especially if you have a solid internal wall you can position it over.)

DettaWalker

Thank you Jeepers - really appreciate the advice. You're a real asset to this forum!

DorsetLad

If you want to measure the mains pressure yourself, it's easy to do. Several suppliers (e.g. Screwfix) sell a water pressure gauge that you screw to the outside tap (which is likely to be connected to the mains). Costs about £15. I found one of these invaluable, since it allowed me to determine that the fairly poor water flow we got from the mains was not due to low mains pressure, so instead must have been due to the old, narrow mains pipes (which unfortunately could not be replaced). As our mains was high pressure / low(ish) flow, when we replaced our vented HW system we opted for an unvented HW cylinder plus accumulator (passive, not pumped), both sited in the garage. We now have mains pressure from the taps and lots of flow, e.g. enough to run a large waterfall shower. 

Jeepers_Creepers

An excellent example of why both pressure and flow need to be considered.

You had poor flow but delivered at a good pressure. This means you were able to use that good pressure to store a tank of 'slow' water under decent pressure, and then use it at will. Perfect solution for you.

If someone had the opposite scenario - decent flow but poor pressure - they could quickly find that their decent flow petered out quickly on upper floors.

Usually, tho', if you have a decent flow coming in, it's usually backed by decent pressure too.

bris

Have you checked you mains stopcock is fully open? A lot of them are set to what people want and not just open fully.

[Deleted User]

DettaWalker said:

Thank you Jeepers - really appreciate the advice. You're a real asset to this forum!


I agree - really helpful and great asset to the forum.  Always grateful for all for the the help given so freely in this forum.

Crimson

DettaWalker

Jeepers_Creepers said:

An excellent example of why both pressure and flow need to be considered.

You had poor flow but delivered at a good pressure. This means you were able to use that good pressure to store a tank of 'slow' water under decent pressure, and then use it at will. Perfect solution for you.

If someone had the opposite scenario - decent flow but poor pressure - they could quickly find that their decent flow petered out quickly on upper floors.

Usually, tho', if you have a decent flow coming in, it's usually backed by decent pressure too.

so interestingly my installer measured the flow & pressure today. Pressure was 3bar at the outside tap in the garden and flow was 16l/m (at 8 AM peak shower time in the road I am sure!), different to my 20l/m I measured at 3PM in the afternoon.
They will have a G3 installer come out to do a proper survey but I guess the low flow isn't very promising.

Jeepers_Creepers

3bar and 16lpm is just about adequate.

The pressure part - 3bar at peak time - is pretty good, tho', so if you did need to fit a 'booster', good chance you'd get away with a passive type which doesn't use a pump, but instead employs that pressure to store the water under pressure against an internal expansion vessel. Challis do these. Once the water is stored, it can be then released at pretty much any rate you want - 20, 30, even 40 lpm - driven by that stored 3 bar.