Boiler overflow into washing machine

If done correctly, YES.
Though I must say your OP is misleading and got me worried.

 

If done correctly, YES.
Though I must say your OP is misleading and got me worried.

 

How does the W/M waste fit in there too?

 

The condensate pipe could have been fitted with a clamp or the waste pipe could have been teed so condensate and washing machine have their ''space''. As it is now, WM waste pipe will struggle to fit in there with ease.
What make of boiler is it?
Has the tenant had problems before with backflow of waste water into the machine? The discharge of condensate from boiler is not enough to create a problem like the one she envisage. Except there is a blockage in the waste pipe or there isn't enough fall in the pipe, I don't see how the condensate waste will back into the WM. It will, if there is a blockage in the waste pipe.

 

I cannot say for certain whether this kind of setup is 'approved' by boiler manufacturers, but can say with reasonable certainty that there shouldn't be any issue of 'backing up'.

For a start there is an air gap around that waste pipe even when both other pipes are inserted. Then there's the simple fact it would take some pressure to force the water back up in to the boiler. In theory it could happen, but that would need a ridiculous set of circumstances - a blocked waste pipe further down coupled with a blocked entry in to that waste pipe top.

I'd personally have preferred a dedicated condensate waste connection to that waste pipe using a boss or tee or similar. But hey.

I think there is possibly more of a risk of the W/M outflow coursing past that condensate outlet and syphoning the condensate trap empty with the resulting suction? In fact there was a thread on here not too long ago with a guy saying his GasSafe condemned such a setup 'cos he noticed the condensate trap level wobbling when the washing machine was used - and slapped a 'DON'T USE' notice on the boiler until the cove fitted a separate inlet.

I think all he had to do was to add a 'tee' into that vertical waste pipe near its bottom (just above the U bend connection) and then an elbow to take an identical pipe up parallel with the first. The condensate pipe emptied into this one - with the cond pipe end only going in an inch or so, so no risk of hitting W/M water level.

So, I don't know if the current setup it against regs, but I would call it pretty pants. And the plumber a lazy twit.

 

If she is a new tenant and taking advice from her dad, then better not to start off with an argument. It's unlikely to cause a problem. I'd say ask the plumber to attend and tee of the pipe so each of the appliances will have their individual slot to go in.
I'm not conversant with Ravenheat as I do not fit them, so can't say much.
If a condensate pipe clamp were used (say half way down the 40mm waste pipe), and the washing machine pipe fitted to the top of the 40mm waste pipe as usual, then, for simplicity sake, if the waste pipe were to be blocked, the supposed blockage will flow out of the waste pipe and onto the floor as opposed to backing up into the boiler.

 

The other problem you may have is that the condensate is quiet strong and could "eat" through the softer rubber of the washing machine hose

 

I've heard the acidity of the condensate likened to that of a fresh tomato - don't know how scientific or accurate that actually is

Know it can't be discharged direct into the ground or near foundations / brickwork but can it really be that corrosive ?

 

Condensate is acidic.
This should easily be resolved by your plumber at no extra cost to yourself (or minimal cost).
Though not ideal but I fail to see the problem?
Ask him in a nice way to go back there and tee off the washing machine stand pipe (say from mid position or so). He should then run the section of pipe that will be accepting the boiler condensate waste around 100-200mm higher than the section where WM waste will be connected. Job done. Your tenant and her father will hopefully be content with that arrangement.