Replacing a hot water storage cylinder:
Wherever possible simply replace like with like. By taking accurate measurements of the existing inlets and outlets and drawing these up into the forming of either a standard factory made low-pressure copper storage cylinder or a custom manufactured low-pressure copper storage cylinder.
Once your new cylinder is on site. Shut off the cold inlet feed to the old cylinder and place a garden hose on the drain provided. If a drain is not provided ready made you will have to remove the inlet pipe on the downhill side of any valve you can use and connect your hose to this valve.
There are times when you have no choice but to drain the cylinder down after drilling a few holes in the wooden floor to allow the large amount of water to escape underneath into the basement area. Before opening up the cylinder to drain turn off the gas or the electricity power supply. If unsure if you have safety isolated the electrics turn off the mains switch on the meter board and undo the wires this way. Once the cylinder is draining you can disconnect the other top outlets and any wetback connections when completely drained.
For a low pressure cylinder the most piping you may have to replace is underneath the cylinder.
Please note: The topmost hot outflow connection pipe must always travel upwards into the wall away from the top of the cylinder. And it must not have a shut off valve fitted on the hot line going out to exhaust in the open air.
If replacing a cylinder with a wetback connected to a fire your careful measuring will pay off with ease of replacement. These copper lines coming into the cylinder will have to be rehemped also by teasing out the hemp and rolling it on your upper leg under your palm with some spit. Then winding this hemp string onto the end of the copper so that the hemp is sandwiched between the thread on the cylinder and the groove bump crox joint near the end of the copper tube. If replacing a mains pressure cylinder take photographs of the existing set up and buy a new cold feed valve train to replace the worn out valve train already installed at the very base of the mains pressure storage cylinder. There will be instructions by diagram on the valve pack. You may not have access to copper benders so in this case use copper olives and brass elbows to make necessary changes of direction in ½-inch (15 mm) and ¾-inch (20 mm) copper lines. On all of the valve train use teased out hemp and place graphite jointing compound paste on top of the hemped joint to prevent the hemp from drying out. Wind on clockwise as you look at the end of each male threaded fitting etc. Then tighten well.