Low Water Flow and Pressure

[Triassic]

Our new build build is at the top of the hill, the rest of the village is below us. Our water pressure and flow is quite low, the standing pressure is about 2bar, however when we open the kitchen tap in our temporary home the amount of water from the bathroom tap drops to a trickle. As part of the site preparation we installed a new 63mm alkatheme supply to the site.

 

 How are we best addressing this issue? A pump maybe? Or a tank and a Pump? 

[ProDave]

Start by fitting an accumulator, that will maintain the 2 bar pressure until you have emptied the accumulator.

 

A pump would need a break tank and gets messy. you can't just suck water out of the mains pipe with a pump.

[Triassic]

1 hour ago, ProDave said:

Start by fitting an accumulator, that will maintain the 2 bar pressure until you have emptied the accumulator.

How would you go about sizing such an item?

[Jeremy Harris]

3 minutes ago, Triassic said:

How would you go about sizing such an item?

 

 

Depends on how much water you wish to draw off in one go, with no break for the accumulator to recharge.  Also worth noting that an accumulator holds less than half its rated capacity, usually around 40 to 45% of the capacity is water, the rest is the air pressurising the bladder.

 

If you have a 10 minute shower at 10 litres per minute, then a break that's long enough to allow the accumulator to recharge before the next one, then a 300 litre capacity accumulator might be OK.  That will be able to supply around 120 to 140 litres of water at a near-constant 2 bar (if that's the peak inlet pressure), so would run a 10 litre per minute shower for ten minutes with some spare capacity.  If you need to draw off more water in one go than this, then go to the next accumulator size up, a 500 litre one, which will give you a usable capacity of around 200 to 230 litres before needing to recharge, but this will take longer to recharge.

 

Well worth doing some pressure and flow rate checks before deciding what to do though, so you have an understanding as to what your supply actually does through the day.  Fitting a peak-reading pressure gauge (or an ordinary one fitted with a non-return valve and means of bleeding it off between measurements) is a good start, as that will tell you what the peak pressure is.  If you get one of the gauges with a peak reading needle it's easy to just reset that several times through the day to get an idea as to how the supply pressure fluctuates.  Also worth measuring the actual flow rate with a stop watch and 10 litre bucket from a wide open tap.  That should give you a feel for how long an accumulator may need to recharge.

 

 

[Mr Punter]

Where we are the water authority guarantee a flow of 9 litres per minute from a ground floor tap.  Perhaps if you are on mains water the water supplier should be doing something if the flow is below this.

[Temp]

If you plan to have a combi boiler make sure they check the pressure and flow rate carefully.

 

Not sure if it helps but the water companies are obliged to deliver 0.7 bar (some sources say 1 bar) where the supply crosses your boundary. However it's not clear to me how they measure that. eg is it the static pressure (no water flowing) or while you are running all the taps in your house?  If it's just a static pressure it's useless as far as protecting customers. 

 

 

 

[Mr Punter]

I think they do a minimum pressure and a minimum flow rate, both pathetically low.

[Nickfromwales]

At 2 bar, its deffo a 500L. That'll be less dependant on being left between recharges. As, IIRC, you'll still be going for a SA for DHW, you'll not suffer the issues with irregular flow rates equating to equally irregular DHW production from such things as a combi, so the worst thing you'll have is changes in flow rate, but not necessarily in temperature. For eg, your shower would run faster / slower, but not hotter / colder.

It is imperative that you take the outside tap, domestic appliances and WC's off the incoming mains supply BEFORE the NRV that isolates the accumulator, which could see you getting away with a smaller accumulator ( subject to your deemed / known water consumption ).