Single pipe system

[corkeykat]

I've just moved into an old house and much of the heating is in galv iron, single pipe system. It looks like the original system was just gravity fed but over the years extra rads have been connected in copper and a pump added.
The barrel diameter varies from 3/4" for feeds to to the rads, 1 1/2" the main feed up through the floor. I need to replace some of the rads as they are the old cast iron style and not very efficient. Now the circuit is pumped is it OK to reduce down to 15mm copper for the new rads without having a detrimental effect on the flow?

 

[Simon F]

The best advice if you want to make the system more efficient
is to update to fully pumped flow and return setup.

Failing that, try to keep sizes the same, that will be for pipes and valves.
If you do replace any pipes for smaller then the flow will be reduced, and the radiator could fail to heat up because the flow is naturally taking the easier route around the loop.

 

[jtsplumbing]

I think due to the age of the system I would be inclined to remove the old iron pipe, as you don't know what condition it is in, you could end up with all sorts of problems, may be held together with rust.

 

[stevetheplumber]

its a suck and see exercise realy old adapted systems can be tricky to predict what works and what wont you are assuming its the rads that are not sufficent when it could just be the system in general

 

[JAH HEATING]

I'm on a conversion, gloworm fuel saver out an y plan to valliant Eco tech pro.

had to alter pipes to new towel rads, took few boards up an the pipe work is crazy.

looks like a one pipe kind of system, tees into same pipe going to rads, but tees then disappearing god knows where.

im in a bit of tricky situation, me connecting onto this strange system is it going to circulate ?

they haven't the money really for a total repipe

 

[jtsplumbing]

Well I hope that you are going explain the risks to the customer, and get them to sign a disclaimer, are you going to be fitting a inline filter on the system ? with all this old iron pipe & radiators on the system it's a must, what are you doing with the cylinder ? is it suitable for a fully pumped system ? It's no good trying to cut costs on a job like this,

 

[Reg Man]

Galv pipe on central heating I thought was not good, because of increased risk of corrosion/ electrolytic action. Well that's what I thought from my early heating training back in the 1970's, which is why we only used black iron. One pipers are not very efficient, change to a two pipe. Cut out as much of the dissimilar metals as you can.