Leaking HWC question how to test?

my3cents

I've just taken out a 7 year old cylinder I put in new because of a slight damp patch (about a tablespoons worth) at the base of the cylinder. I've some work to do on the solid fuel range that feeds it so with the range out of commission it seemed a good time to do it.

I've not got a replacement yet as I wanted to be 100% sure what the size was because I'm limited for space, so interested in where the leak actually was I rinsed out the old cylinder and examined it as closely as possible and it looks perfect with no obvious sign of a leak.

Now its out I know I can get a direct replacement with all the connections in the same place so its not a big job. iirc I was quoted €280 for a replacement 18 x 42 insulated DHW. Now the DHW may be the give away as to why there is a leak as obviously its heating tap water and circulating it directly through the cylinder (no rads obviously). Another point that may be of interest is that the pressure in the cylinder would be very low because it runs off a head of less than a meter measured from the top of the cylinder so about 2m of pressure at the bottom (3/4 inch pipe work to the hot tap sorts out any flow rate problems from the low head). Original cylinder was rated at 10m.

However before I throw it out is there any sensible way to test to see where the leak was and to double check there is a leak? The inside looks perfect and as there is no lifting of the foam I'm guessing any leak is along the seam a few inches up from the bottom.

Then if I do as seems likely throw it out does anyone know of an easy way to remove the foam insulation so I can open out the cylinder to use the copper?

Pete67

The sensible way to test it is to do a hydrostatic pressure test - basically seal all the ports on the cylinder, completely fill it with water and gradually increase the pressure up to the rated pressure using a suitable test pump - something like this. It is common to add a red or a fluorescent dye to the water to make any leak easier to see under UV light. Once at the test pressure, a valve is closed to isolate the cylinder from the pump, completely sealing it. The pressure should stay constant almost indefinitely if there are no leaks, however even a tiny weep will cause a noticeable pressure drop fairly quickly.

Never use compressed air or any other gas to carry out a pressure test, if the cylinder fails it could do so explosively.

Dtp1979

Re stripping the lagging, of it destined for a scrap yard then they usually take it off. If not, The way they do it in the yard is to slice the foam top to bottom in a few places. Oxy acetylene torch then placed into the top hole and the lagging will fall off. This is what they told me anyway

my3cents

Cheers guys I was going to use compressed air but limit pressure by setting the regulator to 10psi which is about 5 psi below the 10m cert on the cylinder.

However its probably easier to fill with water and stick a hose fitting on one of the inlets and give it a quick on off of our mains pressure from a garden hose with no jubilee clips holding the fittings on.

I thought I might have to resort to heat to get the lagging off I've turned a few uninsulated copper cylinders into sheets of copper joined them together and used them as a decorative feature behind the cooker. The round bottom of one old cylinder I've cut so it makes a decorative boss around the chimney stove pipe.