Upgrading Gas Central Heating System

[Tilly2]

We asked for and received a quote from British Gas for three thermostatic valves to be added to out system. (For some reason, all except the three radiators in the sitting room have thermostatic valves)

The quote has details of the following Hydroflow, Condensulate, Powerflush and Magnetic system filter. £304 approx

When they do a powerflush, do they drain all the water out of the system and then fill it up again? We are on a water meter and I'm concerned that this will be costly, over and above the price of the upgrade.

[gingejbee]

I'm thinking that the cost of water used is going to be insignificant...look at your water bill for the cost per cubic metre....that's 220 gallons!

[bhg481]

Where is your room thermostat? If it's in the sitting room you don't need thermostatic valves in there as the room thermostat controls the temperature. In any case you should always leave one radiator without a thermostatic valve otherwise you can find yourself in a situation where the pump is operating and all the valves are closed so the water can't circulate.
The central heating system doesn't contain vast amounts of water, so flushing it shouldn't cost too much. Without actually looking at our water bill, I seem to remember that water costs around £5 per cubic metre and you won't use that much flushing the system.

[Tilly2]

The 'house' thermostat is in the hall, Bhg, not in the sitting room.

There must be a logical reason why the three radiators in the sitting room don't have TRV's.

Thanks, both. That has made me feel a bit better about having it done.

[Everhelpful]

I would get another quote,British Gas are notorious for being by far the most expensive.

[Dogsbody2]

Yes they drain the system when powerflushing, but it isn't clear to me why they deem this necessary, unless you've asked for it

Even with a hot water tank, a conventional DHW and CH system contains of the order of 50 gallons. The cost of the new water is chicken-feed compared to the excess cost BG will want to charge for this task over the cost from a plumber.

[BRIGHT SPARK]

Get a trusted local plumber to change the valves.When he drains down he will be able to tell whether or not the system needs flushing from the condition of the water.

[melv16]

British gas were nearly £1,000 more expensive for a new boiler. We went with the local plumber.

[Tilly2]

Thank you all. We will try some other quotes.