can i use old 1" and 1 1/4" gravity pipes when converting to fully pumped?

[rolysatch]

hi

i've got a pumped central heating/gravity hot water system. if i was attempting to convert it to a fully pumped S plan system - as you can tell i'm a diyer - can i use the old 1 1/4" flow and 1" return of the gravity system for my pumped hot water or should i take this all out and replace it with 22mm?

any advice appreciated

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[kozak1968]

I am guessing it is iron pipework which is quite old, would be best to replace.

 

[SimonG]

If it's copper, leave it. Although you will be heating a greater volume of water. Depends how much you are wanting to spend.

 

[erpkid]

I would use new and weigh in the old. If imperial sizes you don't need the hassle and old copper is worth a mint. If iron you need this sort of hassle even less.

 

[rolysatch]

thanks for the reply's, yes its all old copper, it wouldn't be a huge amount of work to change the pipes as i was going to fit a new hot water cylinder anyway, and i didn't think about the scrap value of the old pipes which would offset the price of new anyway so maybe i'll change them.

i can get my head around the wiring side no problem with the help of diagrams, as far as the plumbing, is it literally a case of me just splitting the output from the boiler after the pump, fitting the two zone valves and putting in a bypass valve and everything else stays the same? my current pump is a grundfos 15-50 is that adequate to pump the heating and hot water or would i need something more powerful?

my biggest problem i'm trying to figure out is the boiler expansion pipe comes off the hot water as it enters the hot water cylinder which also feeds a bathroom radiator from the loft before going into the expansion tank. from what i've read the expansion pipe needs to be before the pump on a pumped system, so would i have to have a new seperate expansion pipe now, before the pump, and could i still run my bathroom rafiator off it? (i might be getting confused at this pount so correct me if i am)

 

[Dotty]

draw a picture mate, and put it up for us to look at for you.

 

[rolysatch]

ok don't laugh at my "engineering drawing" but it will give you an idea of what i think i have, obviously the radiators on the heating circuitr aren't plumbed in like that but it should give you a roungh idea of what i've got. as you can see i think the radiator in the bathroom runs off the hot water heating circuit.

 

[rolysatch]

so with the help of my drawing:

is it literally a case of me just splitting the output from the boiler after the pump, fitting the two zone valves and putting in a bypass valve and everything else stays the same? my current pump is a grundfos 15-50 is that adequate to pump the heating and hot water or would i need something more powerful?

my biggest problem i'm trying to figure out is the boiler expansion pipe comes off the hot water as it enters the hot water cylinder which also feeds a bathroom radiator from the loft before going into the expansion tank. from what i've read the expansion pipe needs to be before the pump on a pumped system, so would i have to have a new seperate expansion pipe now, before the pump, and could i still run my bathroom rafiator off it? (i might be getting confused at this pount so correct me if i am)

 

[stevetheplumber]

you need to investigate the positioning of cold feed and vent in relation to the pump as the pump will have to go on the flow now where does the cold feed go now you havent shown it on drawing which i assume is the existing set up

 

[secret squirrel]

You could combine the cold feed and vent but agree with steve you need to find the cold feed and it is imperative they're in the correct place.

 

[rolysatch]

i'll have to see if i can trace it back from the header tank in the loft, the boiler and pump etc are all downstairs in an outside cupboard but i only have one return pipe coming through the wall so the cold feed must join up with the radiator return somewhere else in the house but the cold feed is not in the same room as the boiler and pump etc. does that help?

 

[M77]

Hi rolysatch, you would have to run a cold feed and vent pipe from the f/e tank and connect this in before the pump. Don't know how hard this would be? Although you have mentioned replacing the current pipe work to the cylinder so this could be done at the same time.
If not would it be easier to move the pump and valves up near to the cylinder then reconnect the htg there? You could also reconnect the bathroom rad into the htg if didn't want it to be off the hot water circs.
Hard to picture without being there but hope this helps.
Just make sure you connect the feed and vent correctly (no more than 150mm apart, before the pump. Or you could use a 'air sep'.)

 

[rolysatch]

So when you say that they shouldn't be more than 150mm apart, i understand this where they are plumbed in but dies it matter if there course deviates from each other a bit on the way up to the F&E tank or do they have to run parralel no more than 150mm apart all the way up?

Also when ever i see the vent pipe on a diagram it always shows it going straight up vertically to the expansion tank (is that just for the diagram and reality is different?), mine would have to take a bit of a windy route - but always going upwards or horizontal - does this matter?

and finally i've got some very long runs from the boiler to tanks in the loft, what are everyones feelings on using pushfit type pipe instead of copper to help keep the cost down, i could use compression fittings with it if this was considered safer?

 

[M77]

Just 150mm where they connect before pump, Vent can be either vertical or horizontal.
And I wouldn't personally use push fit although there's nothing to say you can't. That's why I wondered about the possibility of moving the s plan up to the cylinder, that would shorten your feed and vent runs.
Presume you have rads on the first floor, not just the bathroom?.

 

[secret squirrel]

Love this post started off giving the impression you had a good idea of what your doing, can I use 1" pipes for this to, HOW do I do this.

Brilliant.

Before you start moaning at me yes, this is a site for free advice blah blah blah, my comment is not meant as an insult just amused me.

Genuinely, good luck with your project.:20: (really like this smiley, I am going to use it soooo much more)