Workaround to pressurise a Combi despite low water pressure

[Ronald Fraser]

Is there a workaround that would enable me to pressurise my Combi t

1bar when the mains water pressure is only 0.75bar ? The combi is working and when heating the pressure rises to 0.9bar. I am concerned that the combi should be operating at the recommende pressure. Some have suggested attaching a 1.5bar shower pump ( with attache water tank). Is there an alternative e.g. water pump that would serv to bring the combi up to 1bar purely for commissioning purposes. There is adequate DHW water flow

-- Ronald Fraser

[Paul Barker]

When the system is cold let the air out of the expansion vessl b opening the schraeder valve (like a car tyre valve). Then open up th filling loop to fill the system up to 0.75 bar. Now shut that, get you bike pump out and pump the air back into the expansion vessel whils watching the pressure guage, stop at 1.5 bar, hey presto

-- Paul Barker

[Christian McArdle]

Get the water company to increase the pressure. 0.75 bar should be below their minimum permitted value.

In any case, nothing untoward is likely to come from running 0.75 bar, unless the boiler is at the bottom of a very tall house. I wouldn't muck around with pumps for a measely 0.25 bar that will have no discernable effect on the operation of the boiler (unless it has a very sensitive low pressure cutout).

Christian.

[Rob Morley]

You could use a car tyre pump (not an electric one obviously), a welly and a bowl of water. Just attach a schrader valve to the filling hose to act as a non-return valve, and fill everything with water before you start pumping or you'll introduce air into the system which will need to be bled, losing pressure again.

[Ed Sirett]

Agreed. You could also let the expansion vessel down to about 0.5 bar. Fill to 0.75 and then pump the vessel up till the guage reads 1.0. However I doubt it's worth it.

Another problem you must be having is getting enough water through the boiler to keep the flames (fully) on?

[John Stumbles]

Garden spray pump adapted to connect to the filling point. You can use this to introduce inhibitor etc to the system too.

But as Christian says 0.75 is close enough for jazz anyway.

[Paul Barker]

There is no requirement for any water company to provide any amount o pressure. All they are required to provide is water to your tap

-- Paul Barker

[Ronald Fraser]

-- Ronald Fraser

[kafkaian]

I would agree with this. In our street we had to start a campaign t get Severn Trent to listen afterwhich they duly sorted something out We still get a reduction is pressure however if there is heavy summe usage. An electric shower with small capacity pump is near useless

-- kafkaian

[Mathew J. Newton]

I wouldn't.

Water suppliers must provide an average of a 7 metre static head (~0.7 bar?) at the customer premises in accordance with the 'Water Supply and Sewerage Services (Customer Service Standards) (Amendment) Regulations

1996' (available at many suppliers aim to raise their minimum to greater than this, and also to provide a minimum average flow rate (10m and 9lpm respectively for Sutton and East Surrey Water).

Mathew