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45 posts


#295947 7-May-2022 19:26
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Calling all home plumber experts.



I have just had a bit of work done at home on the wetback (leaky feed pipe).



The HWC (hotwater cylinder) needed to be drained as you'd expect. it is fed by a header tank.



The issue is now that the hot water is barely flowing in the bathroom (vanity, bath, shower). The kitchen/laundry is fine.



Under the house there's the mess of piping with two red twisty turn valves.(top one is #1 and bottom is #2)



#1 valve will disable hot water for the entire house (trial and error) the other valve #2 resumes hot water in the bathroom, but I'm pretty sure the header tank stops filling in this configuration.



I called the company for thoughts, and got some after hours free advice (vs onsite visit which is super pricey). The advice was that this is probably an air block and we did the finger over the double mixer to push cold water up through the hot pipe to push the air out. We didn't have any luck with this (we heard some gurgles in the pipes but all that happens is the cold that was forced up the hot pipe comes out and we get about 5-6 seconds of actual hot water (good flow) before returning to a trickle/nothing.



I thought i had solved it when I turned on valve number two, but the header tank not refilling made me turn it back off. The header tanks kicks in pretty fast when you run the hot tap.



There is a tempering valve between the taps that get hot water and those that don't.



Any thoughts? :P I'll be getting someone around on Monday, but that means flannel baths until then (grr)



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  #2911455 7-May-2022 22:58
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There is a tempering valve between the taps that get hot water and those that don't


 It’s possible that emptying and refilling the pipes has allowed debris to become lodged in the tempering valve...... this would explain low flow....  I would look to either replace or remove and closely inspect it as a possible source of your issues...


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45 posts


  #2911466 7-May-2022 23:47
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hey Gary, thanks for the reply - yeah this makes sense to me until i open the lower valve in the image, then we're all good (it seems). I just don't have the confidence to know that that valve is meant to be closed or not.



in hindsight, I don't understand how opening the lower valve can cause the header tank to stop working, that just seems illogical. I will double check tomorrow. I know this was turned off to drain the tank, so conceivably, it could have been forgotten to turn it back on.

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Uber Geek

  #2911501 8-May-2022 09:25
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Are you certain the header tank is not filling with both valves on? I wonder if other pipe noise is just masking the sound.


Given those pipes are insulated (well, were!) it suggests they are on the outlet side of the tank, and they are both connected together. Assuming that's the case, then the vertical pipe from the top valve is the hot supply, the pipe curving off the top right of pic is the untempered hot to laundry, and the curved pipe bottom right is the hot feed to the tempering valve. can you follow them at all and see if this is where they go?


Particularly with a low pressure (header tank) supply, it's easy to get several air locks in a pipe - you may need to have several goes at the blocked mixer set to warm trick. Perhaps try the same trick but with another hot tap on elsewhere in the house, or the air in the pipes just gets compressed, rather than being pushed out somewhere (if you have a closed system with no vent).


Are those valves hot when the a hot tap is running? Other possibility is one is the low pressure cold from the header tank to the cylinder, and the other is the low pressure cold from tank to tempering valve.


45 posts


  #2911506 8-May-2022 10:14
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hi Running Man - great question



This was spinning in my head last night, so this morning I went up to the header tank, with that #2 valve on and waited with the bathroom hot tap on. The HT started draining and refilling! it did take about a minute of running before you could audibly hear the tank filling. I was impatient yesterday.



So yeah, i applied some spock logic and figured there's no way this valve could affect the header tank by turning it ON =).



I think we're all good now, bit poor form for the plumber to forget to turn a valve back on and then walk off the job, potentially requiring a revisit that I would also need to pay for (well i would kick up a stink for sure).



thanks all for comments, appreciate it :)



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