draw-off cock technical
draincock

Straight connector fitted with draincock to allow the system to be emptied.

The drawing on the opposite page shows a mains stopcock with a draincock fitted above.

The cold inlet at the bottom of the cylinder can be fitted with a male iron to copper elbow containing a draincock.

Sometimes, a safety valve may be fitted into the boiler flow pipe; a draincock is always fitted in the return.

When refilling the system for the last time, do it via the draincock rather than the feed-and-expansion tank, to lessen the risk of airlocks.

Then shut off the water supply to the feed-and-expansion tank, fit a hose to the lowest draincock on the system, and lead it to a drain outside.

Next, turn off the boiler, programmer and immersion heater, close the stop tap supplying the feed-and-expansion tank, and open the draincock.

Unlike the other three types of valve, a drainvalve (or draincock) is usually kept closed and opened only when the system is to be emptied of water.

I dont know if that is what he did but after various noises of brakes and draincock steam we started to move up the hill slowly; no faster than walking speed.

No valves should be fitted to obstruct the cold feed pipe to or the open vent pipe from the boiler - apart from a draincock at the lowest point of the system.

Attach a hose to the system draincock, tie up the ballvalve arm in the feed and expansion tank, then open the valve, draw off two or three buckets full of water, and close it again.

These vacuum pumps are very reliable and need very little attention, the filter needs to be cleaned occasionally, the sediment chamber draincock opened very more occasionally and a check to see that all joints are airtight.

Refill it by closing the draincock and restoring the water supply to the feed-and-expansion tank, and turn the system back on so you can pump the clean water round again and remove the last remains of the descaling.

The old tank can usually be drained from the draincock at the boiler or gas circulator (after turning this off): make sure that the gatevalve on the cold water supply to the hot water tank is closed before you do this.

This will necessitate turning off the water supply at the main stopcock, and opening all the cold taps to drain the cold water cistern; then you'll need to attach a hose-pipe to the draincock next to the hot water cylinder to drain this.