Unvented cylinder help.

[Ixia]

I'm only a sporadic visitor, but I'm hoping someone can help me with this.

In our last couple of houses, I've done a lot of the plumbing (replacing bathrooms/kitchens etc.) Our new house has an unvented cylinder (Santon PremierPlus solar) and I want to replace the cloakroom sink, do I have to drain the cylinder and how? Previous houses had a combi boiler and I'm regretting being talked out of having one again, as I'm finding the unvented system a bit of a worry.

Thanks.

 

[MattW]

No need to worry - you can ignore the unvented cylinder to do this.

If you have a pump that circulates hot water around the house (some large or tall houses do), make sure that you turn this off first as they can burn out if turned out without water in the pipes. Then just turn off the mains stop cock where it enters the house and then open the taps at the lowest basin or bath in the house . This will drain the hot and cold water pipes through out the house. Then change the taps as you would normally, turn the mains back on and the pumps if necessary.

The cylinder will remain full through out this process as water can't exit the unvented tank if water (or air) isn't flowing in to take its place, which can't happen as long as the mains inflow pipe is left in place.

If the cloak room is the lowest point just make sure you have a towel to hand to mop up the small about of water that will be in the pipes below the taps that can spill out when you move them.

 

[MdB]

If your sink doesn't have isolation valves to make this job easy then make sure you fit them whilst you do the job. If it does have them, then obviously you don't need to drain the system.

Depending on where there are stopcocks and non return valves in your system, if you drain the cold water, this may or may not drain the hot water as well and it may or may not drain the hot water tank. I've set up my new system so that it is possible to isolate the part you want to work on and I've also installed drain points at the lowest points so it is easy to drain down completely.

It would be worth your while to draw up a diagram of your system so that you know what is going on. Also check out the installation manual for your tank (such as this: http://www.ferroli.co.uk/product_documentation/Cylinders/Cylinder_Installation_Manual.pdf) which will give you a diagram of how it should be laid out.

 

[middi]

Before you worry about draining the system, if you are lucky, a self respecting plumber may have fitted in line stopcock valves just below the hot and cold taps. Just turn these off, do what you need to and turn them back on again.

 

[Flyfisher]

I don't know if you're planning to use those short flexible couplings between the fixed water pipes and the basin taps but I recently discovered that they are available with built-in isolation valves, which seems an ideal solution.
http://www.screwfix.com/prods/18417/Plumbing/Flexible-Hoses/Flex-Tap-Connector-Valve-15mm-x

 

[Jon Maine]

You can try for airlocking the system as described above, check for service valves under the sink or even just buy an aerosol of pipe freezer, cut the pipe put in a valve then do your plumbing at leisure.

http://www.diy.com/diy/jsp/bq/nav.jsp?action=detail&fh_secondid=9271700&ecamp=trf-005&CAWELAID=266881214

 

[MdB]

I'm not sure I would do the plumbing at my leisure if I used a freezer spray...

 

[chuckey]

If you resort to freezer spray, crush the pipe slightly where you are going to freeze it, if you don't the ice plug can slide out (apparently) and its possible that you have to wait for your wife to come home with your finger over the end of the pipe before things can be sorted out.
Frank

 

[FamilyWiggs]

its possible that you have to wait for your wife to come home with your finger over the end of the pipe before things can be sorted out.
Frank

I think that could have been phrased a bit better Frank! :wink:

 

[Jon Maine]

I'm not sure I would do the plumbing at my leisure if I used a freezer spray...

I said

pipe freezer, cut the pipe put in a valve then do your plumbing at leisure.

I wouldnt suggest doing it at leisure before putting the valve on :lol: Should only take around 2 -3 minutes to cut the pipe and put on a ballofix after freezing.

Of course its much easier using my Rothenberger pipe freezing kit....

http://www.mytoolstore.com/roth/freeze01.html

 

[Aidan]

Installation and maintenance instructions are available here;
http://www.santon.co.uk/docs/Premier_Plus_Solar_-_Issue_4_-_36005945.pdf

If there are no service valves, you should be able to shut the isolating valve on the cold feed to the cylinder and drain the hot pipes by opening a tap. The cold enters at the bottom of the cylinder and the hot comes out the top, so you shouldn't need to drain the cylinder.

If you do drain the cylinder, with the drain cock (that should be) on the cold feed pipe, ensure that some hot taps are opened to allow air into the cylinder. The cylinder can otherwise become an ex-cylinder very rapidly (one for Graham's Top Tips).

An unvented cylinder is far preferable to combi for 95% of houses. The risks of bursting are exaggerated with the multiple safety devices; most of the world uses them with few mishaps.

 

[Ixia]

its possible that you have to wait for your wife to come home with your finger over the end of the pipe before things can be sorted out.

I am the wife :lol:

Thanks for the advice, unfortunately Christmas got here first and now the guests have been and gone (and seen the horror that is my cloakroom) I've lost the impetus to do anything with it.....