Low Mains Pressure to my Santon Premier Plus
- Thread starter Trigg
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B
BigBurner
Can anyone explain how an accumulator works
From this site http://www.heatweb.com. Click on "accumulators" on the right hand side.
The flow of water to taps from a mains fed system is limited by the size of pipes and fittings that the water has to flow through. Where you have no restrictions, and large pipes, it is possible to get a large flow, even with a low pressure.
The problems start when pipes are smaller that desired, and act as a restriction. Old mains supply pipes into properties are typically 1/2 inch and even with a good pressure the water simply cannot flow through the pipe in great quantities.
To the user this is seen as a severe drop in flow rate from a tap when a second tap is opened simultaneously. There is not enough water coming in to do both, so it gets shared.
An accumulator is a simple fix. It is a water vessel containing a balloon of pressurised air. The mains water squashed the air as it fills the vessel, until the air pressure increases to match the mains supply pressure. Now, when a second tap opens up, the additional water required can be supplied from the vessel, at full mains pressure, without the restriction there is on the mains supply.
When all the water charge in the vessel has gone, the system returns to normal flow rates, so it is important to estimate the size you will need based upon how much water you may need before all taps shut and the vessel can recharge.
Installation could not get any easier, with one connection anywhere into the cold mains pipework. A non-return valve is also needed on the incoming mains to prevent the charge from disappearing back into the mains supply should the local pressure drop temporarily.
They are maintenance free and DIY installable, and with typical prices around the £200 mark, you are unlikely to find a cheaper way to improve your flow rates to taps.
The most common sizes are 100 and 200 litres. Prices on request.
You half the size for water content. 200 litres, gives 100 litres of water.
B
BigBurner
Great stuff, thanks BigBurner, very informative site
An accumulator stores cold water, so a reserve in a cut.
Some take the kitchen tap and outside tap before the non-return valve on the maintap. This means the kitchen tap is not off the accumulator. If you are having a shower and the kitchen tap is turned on, you are not affected in the shower and the kitchen does not take the reserve of water.
Smaller, cheaper accumulators can just supply the outlets that are needed: cold on the shower & bath and all DHW. The others may not need high flows and pressures. A toilet clearly does not, but you may want the reserve to supply the toilet in an outage. Up to you want you need off the accumulator. The bigger the accumulator the more you pay.
Beware! They can be as large as an unvented cylinder. When one is needed a high flow combi is nearly always the best cost effective way, as it gives the flows and saves space. You are going to have a boiler, cylinder and an accumulator. That is a lot of space taken up.
The accumulator can go in a garage. I have fitted smaller versions only doing the DHW and cold of bath and shower, and put them in the garage loft with strengthening.
The useful output volume provided by an accumulator varies widely according to a complicated interaction between the mains supply static pressure and the minimum presure that the showers etc, will still operate at and always aided by the flow rate which the bare mains supply will provide.
The higher the static pressure the more useful volume. If you assume the minimum useable supply pressure is say 1 Bar then 3-4 Bar supply pressure will give you up to about 80% capacity.
On the other hand if the supply static pressure is only about 1.2 Bar, as in a third floor London flat, then you could find that only 30% of the store volume is useful.
You need to very carefully assess the duration and flow rate of the shower etc. to assess the smallest manageable store volume.
A Megaflow unvented has an air bubble which gives a small accumulator effect.
Tony
The mains water static pressure (eg; 1.2 bar) is largely addressed by the proportionally lower static air pressure set up in the accumulator upon commissioning.
Very little of the incoming water flow is used when drawing off from an accumulator, because in use the dynamic pressure of the water main is below the dynamic pressure supplied through the accumulator, due to the difference in flow rates.
Only when the 'boosted' flow from the accumulator is nearly exhausted will the dynamic pressures start to equalize.
Very little of the incoming water flow is used when drawing off from an accumulator, because in use the dynamic pressure of the water main is below the dynamic pressure supplied through the accumulator, due to the difference in flow rates.
Only when the 'boosted' flow from the accumulator is nearly exhausted will the dynamic pressures start to equalize.
Technical stuff
I have 1/2 inch incoming pipe from external water meter to kitchen stop-cock (approx 9m run), then 15mm pipe feeding the Santon from kitchen to upstairs airing cupboard (approx 8m run).
Having all this new information, I now plan to check my water pressure and flow rate at the kitchen sink or external tap, if necessary I can replace the 15mm feedpipe with 22mm (even though I have fitted a new kitchen I think I can still access the pipework!) I may even be able to upgrade the 1/2 inch pipe outside because the driveway needs digging up soon to lay a drain pipe. If this doesnt solve things I can install an accumulator either buried in the drive before the kitchen stop-cock or maybe install a small one in the airing cupboard to feed the bath shower and santon.
Does this sound ok?
I have 1/2 inch incoming pipe from external water meter to kitchen stop-cock (approx 9m run), then 15mm pipe feeding the Santon from kitchen to upstairs airing cupboard (approx 8m run).
Having all this new information, I now plan to check my water pressure and flow rate at the kitchen sink or external tap, if necessary I can replace the 15mm feedpipe with 22mm (even though I have fitted a new kitchen I think I can still access the pipework!) I may even be able to upgrade the 1/2 inch pipe outside because the driveway needs digging up soon to lay a drain pipe. If this doesnt solve things I can install an accumulator either buried in the drive before the kitchen stop-cock or maybe install a small one in the airing cupboard to feed the bath shower and santon.
Does this sound ok?
All your suggestions sound sensible and in the right order.
I would ask your local water company to give you an informed speculation on the likely flow rate you could expect by renewing your water incoming main. As MDPE is cheap, if you take this option, a larger size would be sensible, eg 32mm.
However, we would not advise you to bury an accumulator, because they are not corrosion proof. A plastic bodied unit is under evaluation, we are told by the UK licensee, but this may not be available any time soon due to some issues.
I would ask your local water company to give you an informed speculation on the likely flow rate you could expect by renewing your water incoming main. As MDPE is cheap, if you take this option, a larger size would be sensible, eg 32mm.
However, we would not advise you to bury an accumulator, because they are not corrosion proof. A plastic bodied unit is under evaluation, we are told by the UK licensee, but this may not be available any time soon due to some issues.
B
BigBurner
Who is the maker? Plastic on cold water is fine. On hot? No, no!
It would not be very much work to expose your external stopcock and disconnect your side of the stopcock and temporarily measure the open pipe flow rate that can be achieved at that point.
With a few more bits you could measure the dynamic flow/pressure. Thats simply the flow rate you get through a restriction ( tap ) whilst having a remaining pressure of say 0.5 Bar or 1 Bar before the restriction.
If its good at the point then merely upgrading the supply pipe to 32 mm will probably be sufficient. Otherwise it means a new street connection. If you are getting rid of all lead then some suppliers used to do that free but most charge about £400+ now.
I recommend taking the 32 mm right up to the Santon with no elbows, that means gentle curves as every elbow is a restriction. Tee off for other connections.
Tony
With a few more bits you could measure the dynamic flow/pressure. Thats simply the flow rate you get through a restriction ( tap ) whilst having a remaining pressure of say 0.5 Bar or 1 Bar before the restriction.
If its good at the point then merely upgrading the supply pipe to 32 mm will probably be sufficient. Otherwise it means a new street connection. If you are getting rid of all lead then some suppliers used to do that free but most charge about £400+ now.
I recommend taking the 32 mm right up to the Santon with no elbows, that means gentle curves as every elbow is a restriction. Tee off for other connections.
Tony
B
BigBurner
Are you serious? Blue plastic pipe can't be fitted overground. And 32mm to the UV cylinder? Have you ever fitted or sized one of these?
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