Routing condensate pipe new boiler install

Hi looking for adivice re a new boiler installation. Have been given different adivce from different plumbers re routing of condensate pipe.

I thought it could be joined up to the bath waste (just the other side of the wall) however bath waste runs on a fall to end of bath then looks almost horizontal to the main waste stack.

Never had any issues with drainage.

Plumber one says condenste will be boiling is likely to sit in and damage pipes causing leak in future.

No mention of acidity of the condensate.... is that not an issue in plastic?

Plumber two says this solution would be fine. Only risk is if there is a blockage condensate waste would likley come up in the bath.

This got me thinking, but not in time to ask, what if there was a blockage could bath waste be pushed back up to boiler and cause damage? (There is an approx 1m drop boiler to bath) never had blockage in many years lived here but always a first time.

Plumber 2 said an internal solution is always preferable to external which is the alternative given by plumber one. Ie a waste pipe running down beside my back door.

Is there a right way or is it just personal preference?
Is what plumber one said a valid concern, plumber 2 said it wasn't?
Should i be concerned about bath waste back flow to boiler?

JDD44 said:

if there was a blockage could bath waste be pushed back up to boiler and cause damage?

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No, if the bath waste was blocked first you would see water left in the bath and no way would that water be lifted 1 metre up to the boiler.

If the condensate pipe was blocked and the condensate could not leave the boiler then the boiler's safety system would ( should ) shut the boiler down.

JDD44 said:

acidity of the condensate.... is that not an issue in plastic?

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No the slight acidity will not harm plastic pipe, and the condensate is not boiling ( unless there is a serious fault in the boiler )

An internal run is always better as an external run has the risk of freezing in cold weather and that will prevent condensate leaving the boiler which, when flooded with condensate will ( should ) shut down

plumber number 2 is right,
if your bath water drains away with no problem the little amount of condensate water will do the same, it's not boiling water, it's luke warm at best. It is acidic and that's why it's usually run in plastic because nothing destroys plastic!! (as we all should know by now)

if you're worried about it backing up to your boiler (which is highly unlikely) fitting a non return valve on the condensate pipe won't hurt: https://mcalpineplumbing.com/traps/...tings/convalve-line-vertical-non-return-valve they're about £10 and it goes inline on the pipe.

What @gasmanstu72 says