10mm limestone chippings for soakaway

tomasrojo

Hi, not sure if this is the correct forum, but it's related to a new oil condenser boiler, so maybe.

The nearest drain was too far away for the condensate outflow, so I'm installing a soakaway. I have the unit itself (one-ended plastic tube with holes near bottom and lid for top) and the piping, but I just can't get the 10mm limestone chippings to backfill around the unit to neutralise the acidic condensate.

I've looked in quite a few builders suppliers and DIY stores around the Sandyford Industrial Estate, but I'm willing to travel a bit further, provided it's still in Dublin.

Anyone know a place that stocks them?

Also, just out of curiosity, the instructions with the soakway say to fill the tube with limestone chippings, while other advice online says not to, and just backfill. Is it all that important? I was going to follow the instructions that came with the unit.

tomasrojo

The boiler was installed by a professional and certified too, by the way, but the man who certified it recommended a soakaway with limestone, rather than a French drain-style hole with rubble and gravel, which I currently have.

I think I only need 10 or 20kg of chippings. Enough to mostly fill a cylindrical hole about 30cm deep and 15cm wide.

anthonyos

Try a garden centre

tomasrojo

anthonyos wrote: »

Try a garden centre

Thanks! I did try the garden-related bit of Woodies, but they only had quartz and granite.

I'll have a look at a few dedicated garden centres.

Wearb

Did you try Chadwick's or Heatmerchants. If they havent it, they might advise.

tomasrojo

Wearb wrote: »

Did you try Chadwick's or Heatmerchants. If they havent it, they might advise.

I did (bought the soakaway itself in Heatmerchants), but they don't do limestone.

Heatmerchants mentioned a quarry in Cabinteely (could be totally wrong about this) or something, but I didn't get a chance to write it down and forgot it then. Someone else I know mentioned Roadstone in Belgard, but I emailed them and didn't get an answer. I should phone them. I'm willing to go a bit further than I've gone, but only if I'm sure I'll be able to get the chippings on the other end, as I'll probably be cycling there with a trailer, so I don't want a wasted journey if I can help it (I can also rent a car if I have to go outside County Dublin, but it's starting to get too expensive at that stage). I was directed to Brooks by Chadwicks, and Brooks directed me to a quarry in Wicklow, but I looked them up and they don't seem to do limestone.

thegardenshop.ie do them, but only by the tonne, which rather exceeds my modest requirements.

Wearb

Wait until evening for some of the lads on here to read your request. Some of them in your area might know of a place nearby.

tomasrojo

Thanks! Appreciate the advice.

I'm ok with a round trip of up to about 40km, but after that I think the effort might be too much.

RJF

Just Google limestone chippings dublin???

https://www.google.ie/?gws_rd=cr#q=limestone+chippings+dublin

B and Q also do them.

Worst case go to a local building site and ask for a wheelbarrow of hardcore and put it in a couple of bags.
Most lads are fairly helpful.

Calahonda52

Are we all sure about the science here as a permanent solution

to neutralise the acidic condensate.

I am not for the following reason.
Rain plus Carbon dioxide gives carbonic acid: H2CO3, which is what gives us limestone caves.

The acid formed, H2SO3 and others, in the boiler is far more aggressive so it will just dissolve the limestone in time

Wearb

Calahonda52 wrote: »

Are we all sure about the science here as a permanent solution

to neutralise the acidic condensate.

I am not for the following reason.
Rain plus Carbon dioxide gives carbonic acid: H2CO3, which is what gives us limestone caves.

The acid formed, H2SO3 and others, in the boiler is far more aggressive so it will just dissolve the limestone in time

What is produced in the interaction between the condensate and limestone?

RJF

The condensate is similar acidity to vinegar.
In a SOAKAWAY rain and moisture dilutes the acid.
Same with drain.
We would be a long long time waiting for the limestone to break down.
A lot of boiler lifetimes.

Wearb

RJF wrote: »

The condensate is similar acidity to vinegar.
In a SOAKAWAY rain and moisture dilutes the acid.
Same with drain.
We would be a long long time waiting for the limestone to break down.
A lot of boiler lifetimes.

I know that the limestone being alkaline neutralizes the acidic condensate. What I was curious about was what was produced in this interaction?

RJF

The acid neutralization occurs when the acidic solution comes in contact with the limestone.

The calcium carbonate in the limestone changes the solution into water, CO2 and various (mineral) salts.

All lime and limestone (marble) contains different percentages of calcium carbonate so making totally accurate capacity statements is not realistic.

tomasrojo

Hi! I did Google (and DuckDuckGo), but not too much came up that seemed immediately helpful. I saw that B&Q in the UK did them, but my wife rang them here and they said they didn't.

I think the acid in the condensate is sulphuric and nitric acid, so I guess the interaction with limestone would produce calcium nitrate and calcium sulphate (and water). But that's just off the top of my head. I'm guessing the comment about the limestone being good for the lifetime of several boilers is correct.

Thanks for the tip about hardcore. Will look into that. I'm going to try a few garden centres too.

tomasrojo

Roadstone emailed me back and say they sell 14mm grey pebble in 25kg bags, €7.00 per bag. I'm just double-checking that it's limestone. If it is, I'm sorted.

tomasrojo

I'm sorted. It is limestone.

Thanks for all your answers! Very helpful.