combi boiler hot water pipe mods

[harbottle]

Hi I have a Worcester Bosch 30I combi boiler, the domestic hot water pipes get to my taps by travelling half way around the house so I want to alter them to make the route shorter and get hot water faster and more economically. My question is to do this do I have to drain my whole heating and water system or can I just turn off the cold water, drain the hot water and make the mods.
Thanks

 

[ianmcd]

no need to touch the heating system, isolate the cold water inlet under the boiler and open a hot water outlet(lowest one is best) until water stops, you might still have some water within the pipe though so be prepared for some to come out when you cut the pipe

 

[harbottle]

Thanks for your reply Ian, that's what I thought but it's good to get advice from an expert.

 

[hard-work]

General points for mains pressure systems (combi and unvented cylinders):

1. Fit a dedicated 22mm cold feed to the combi from the stopcock, irrespective of bore size of mains pipe. This assists in giving flow priority for the shower;
2. Fit a full bore main stopcock;
3. Dedicated hot pipe to showers from combi/unvented cylinder;
4. Fit combined isolators/flow regulators (using a cartridge for litre/min) on all H&C outlets - to *balance* the system;
5. You could use hot and cold manifolds with pipes to each outlet from each manifold.

Then only 12mm pipe need be fitted to most outlets - 15mm for the showers. In softer water areas, even smaller bores. This gives quicker DHW delivery at the taps as the volume of cold water in dead-leg pipes is less. Doing the above makes a big difference improving flow and influence of outlets being turned on when the shower is operating.

The above always works. I can personally testify as my place is piped up that way. I see 5. above a lot in France in new builds. They use the equiv of 8mm, 10mm, 12mm and 15mm from the manifold. As the pipes are small bore, with low cold water dead-leg in the pipe, the delivery of hot water to the taps is fast. We can learn a lot from the French.

I have lost count of the times I have seen an old flow restricting stopcock with a 15mm pipe coming off it snaking around the house to all cold outlets with the combi teed off in 15mm, like it was just a tap! And they can't figure out why the Hot & Cold water system is poor. The flow in marginal installations with poor flowrates can be improved. Especially the irritating cold slug influence of one tap over the shower (shower is king and must get the bulk of the flow). It is taking out flow bottlenecks and balancing the H&C water system. Do you need full flow in basins, washing machines, dishwashers, toilets, etc? The answer is "no". An extra 5 minutes on a dishwasher or washing machine cycle because it is filling very slowly makes no difference whatsoever. Direct the scarce flow to where it should be, which is usually the important shower.