Installing automatic bypass

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Hi all,

I'm considering replacing our old manual bypass valve with an automatic one.

Is it possible to do this without draining the system?

We've just had a new boiler fitted and inhibitor added so I'd rather not drain it unless I have to.

Please see photo. If I close the zone valves, the pump out valve and the hot water return valve, would this isolate the bypass valve so I can cut out and replace it? Or would there still be some pressure?

Also would it make sense to replace the 15mm bypass pipework with 22mm? We get a fair bit of flow noise on pump overrun so I'm hoping swapping for 22mm with the automatic bypass would solve this?

Thanks in advance,

Rob
 

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If I close the zone valves, the pump out valve and the hot water return valve, would this isolate the bypass valve so I can cut out and replace it? Or would there still be some pressure?

There would be as you're not isolating everything - the returns are still connected and "live" (the pipe going below the floor). Why do you think it needs an automatic one?
 
Thanks - I thought that would be the case and can't see how I could lock off the return side as there's no valve that I can see.

Main reason I'm thinking of replacing it is that during pump overrun it's rather noisy, makes a high pressure hissing sound, presumably as it's having to force the output from the pump through a barely cracked open gate valve and 15mm pipework (wheras the rest is 22mm). I also gather a manual valve isn't very efficient, as it's always giving up some flow to the bypass, even when the CH/HW are on, and as we've just had a new boiler fitted I thought it might be worth updating.

Do you think it's worth doing? Would it get rid of the overrun noise? Or would I get the same result perhaps by cracking open the bypass valve a touch? My concern then is it will be even less efficient. Automatic does seem to make sense.

Is there any way I can isolate it without draining the system. If I close off all the valves mentioned then it's isolated from all angles except that return that goes into the floor as you say, might there be a valve somewhere else in the system that would close that off?
 
The auto bypass should have been fitted as part of a new boiler install, unless there's already one in the boiler (ie: Vaillant 6 series).
 
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Yep, I'd agree with that now I know what a bypass is! Boiler was fitted a couple of days ago and I didn't know what a bypass was until I read into it yesterday. I knew the system was making a noise on overrun and thought that the new boiler might sort that but it hasn't (which is obvious now I know what a bypass is). I do feel that the installer should have at least raised the issue and offered the option to upgrade it (even at extra cost) while he had the system drained down but he didn't. It's a Worcester Bosch 24ri, is this something that would invalidate the warranty?
 
Worcester ask for an auto bypass to be fitted in an S plan layout, which you have.

Therefore the boiler has not been fitted to instructions; hope it was very cheap because chances are nothing else would have been done properly, like powerflush, gas pipe sizing etc.

Decent Honeywell or Danfoss bypass is around £35 upwards. If you go to the merchants and say whatever's cheapest, you can pay a tenner. Your bloke couldn't even stretch to that.
 
To be fair to the guy he works for a larger company and presumably his remit is to do what's been spec'd and avoid getting roped into anything else! If he'd been independent I imagine he would have raised it and "upselled" the auto bypass, which I would have gone for if the price was right. If anyone is culpable it's the sales guy who came round and did the quote, got the impression he'd been in the trade so I'm suprised he didn't notice it. I may well give the company a call and see what they say, but I don't imagine getting them out again will be the quickest/simplest/cheapest option!

Gas pipe is 22mm, they fitted a magnetic filter and as I understand it the benefits of powerflush are debatable. They offered it up but it seemed like a needless expense so I passed. As far as I know we don't have a sludge problem.

Anyhoo, back to my original question, is it possible to isolate and replace the bypass valve without draining the system?
 
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The benefits of everything are debatable. Bypasses, filters, power flushes, vegetarianism.

The answer to your question was provided in the very first reply. Which you could also debate if you wish.
 
If you're trying to catch me out I think you've succeeded ;) But I'm still not sure what to do about this valve (if anything).

What would you do in my situation? Drain down and replace the valve with an auto or leave as is and perhaps crack open the valve a touch to reduce the pressure/noise on overrun?
 
Close all upstairs radiator valves and then drain from the boiler. 90% of the water will stay in (downstairs won't drain at all) and you won't need to re-dose with inhibitor.

Worcester will NOT invalidate warranty for no auto-bypass... A manual bypass is not ideal but not enough to invalidate warranty. No bypass at all might be a different story.
 
Now we're getting somewhere - thanks St0rmer66.

Would it make sense to replace the 15mm bypass pipework with 22mm while I'm there, or not necessary?
 
15mm should be fine. 22mm would mean unsoldering joints etc and especially annoying to do on painted pipes!

You will struggle to find a 15mm bypass though... most I see up size to 22mm for a short section either side of the valve.
 
Thanks, happy to get the torch out and put the effort in if necessary! One of the reasons I'm doing this is to eliminate the flow/pressure noise, is there a chance the 22mm to 15mm reduction is causing this or is it more likely just because the gate valve is only opened a crack (so as not to waste too much flow when CH/HW on) whereas an auto bypass will open fully during overrun and hopefully eliminate the pressure/noise?
 
Thanks, happy to get the torch out and put the effort in if necessary! One of the reasons I'm doing this is to eliminate the flow/pressure noise, is there a chance the 22mm to 15mm reduction is causing this or is it more likely just because the gate valve is only opened a crack (so as not to waste too much flow when CH/HW on) whereas an auto bypass will open fully during overrun and hopefully eliminate the pressure/noise?

More likely because the manual bypass is only open a crack.

Replacing with correctly set auto bypass should cure your noises
 
Excellent, I'll give it a go with upsizing to 22mm either side of the auto bypass, and if that doesn't cure the noise I'll bite the bullet and go back and replace with 22mm, but sounds like it will be fine.

Many thanks.
 

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