No water from the hot water taps after draining system

[Rollerball]

Today I needed to replaced the cartridge on my kitchen sink mixer tap, and because the installer didn't fit valves on the hot and cold pipes to the mixer tap I had to turn off the water at the mains and drain all of the hot and cold water from the pipes.

I've now re-fitted the old cartridge to the mixer tap (another cartridge is now on order) but even though I've turned the mains water back on I can get plenty of water from the cold taps in the property but barely anything from the hot water taps.

If I leave it for a while then turn on a hot water tap then some (cold of course) water comes out, but this reduces to a dribble after a few seconds then stops.

I've been into my attic and checked the cisterns and both (a large and a small one) are full.

This indicates to me that something is (very slowly!) filling up somewhere, but where?

I'm really baffled - I would have thought that I would at least get a steady stream of cold water from the hot water taps.

Any ideas please? Or do I need to leave it for a few hours?

I've also just turned on the hot water heating on my boiler to see if that helps in some way.

Thanks

 

[HERTS P&D]

Do you have a wet vac?


If not place your hand under the spout and turn on the hot water tap, then open the cold slowly. This will push cold water up the hot water pipe, hold this position for 30 seconds. Then turn off the cold and remove your hand.

Andy

 

[Rollerball]

Thanks - what's a wet vac?

This is an old property so i guess not?

Also, you mentioned about turning on the hot water tap then slowly opening the cold, but do you mean on any tap or just the mixer? (the other taps are all separates in the bathroom (sink and bath)).

Edit: I can now get a steady slow flow from my bathroom hot tap (it's hot too seeing as I turned on the boiler hot water a while ago) but then there's nothing from the bathroom and kitchen hot water taps.

 

[HERTS P&D]

Close all the taps in the house, then place your hand under the kitchen mixer and open the hot side, then open the cold slowly letting cold water up the hot water pipe. Do this for at least 30 seconds.

Andy

 

[Rollerball]

Thanks, but no luck with that.

However, the water IS now flowing well in the bathroom - I got this going by turning on only the bath hot water tap - this came out in a steady but slow dribble which slowly increased over a period of a few minutes. The bathroom sink hot water tap then started to work well. But still no water from the mixer tap in the kitchen when set to hot (it's one of those taps where you move the single lever left for hot and cold for right and lift up to switch on).

It's worth pointing out that when I was draining the hot water system earlier it was the hot water in the kitchen's mixer tap that stopped flowing first; that stopped flowing at least five minutes before the taps in the bathroom had completely stopped.

Also, when removing the mixer cartridge the top part came apart - I'm certainly I've reassembled it correctly, and it's worth noting that if I leave the hot water mixer tap off for a few minutes then switch it on it will come out in a very slow dribble for a few seconds, then stop.

When the hot water system was being drained the fact that the kitchen mixer tap was first to stop presumably means it will be last to come back?

But how to get it flowing?

 

[Jackrae]

Perhaps an explanation would help you

A wet vac is a wet and dry vacuum cleaner.

Basic problem is that air has got into your hot pipework and because of hydrostatic heads created in bends, loops etc there is not enough pressure produced from the header tank to "push" the water through the system.

If you have a wet and dry vac you could try and suck the water to the tap by turning on the hot then placing the suction hose onto the outlet (whilst forming a seal by cupping your hands over any loose openings. If this works you'll soon know as you'll hear the water running through. After that syphonic action will keep water flowing correctly.

If you don't have a wet and dry the other technique is to backflush the air out of the system by forcing some cold water back up into the hot system. This can be done on a mixer tap by turning on the hot tap, holding your hand over the outlet to block it, then partially turning on the cold. This will backfill the hot line. You have to be careful not to overdo this as you could end up overfilling your header cistern and (if you don't have a good overflow pipe) flooding the attic.

 

[Rollerball]

Ah ha, that worked this time. Must have been doing it wrong before - all is well thanks (and no apparent flooding in the attic!).

Thanks for everyone's help with this.

As I still need to change the cartridge in a few days I'm now wondering what should be the proper way to get the system going again as I will of course have to drain it once more. This time it was a matter of experimentation and people's help here.

Perhaps the order should be:

a) Turn on hot water tap in bath
b) Once the bath water is flowing there, turn on hot water tap in sink in bathroom
c) Use the method in earlier messages to get the hot water flowing in the mixer tap in the kitchen.

Does that sound right?

Also, regarding the potential for flooding the attic - the overflow pipes from the attic cisterns work well (as far as I know) but presumably there is only a risk of an overflow when I'm doing the backflush and not once the backflush has worked?

 

[Blagard]

When you drain it again, stick some isolation valves below the sink on the supplies so you can turn them off locally!

 

[EFLImpudence]

Do you not have a hot water isolator somewhere?

 

[Rollerball]

When you drain it again, stick some isolation valves below the sink on the supplies so you can turn them off locally!

I like that idea, but is there an 'easy fit' type of valve that doesn't involve pipe cutting and soldering?

 

[Rollerball]

Do you not have a hot water isolator somewhere?

Afraid not - at least nothing that I can find that would just cut off the hot water supply to the kitchen tap.

 

[Blagard]

I like that idea, but is there an 'easy fit' type of valve that doesn't involve pipe cutting and soldering?

These are about as easy as you can get - push fit, but you do want a pipe cutter to make it easy so second link is about as basic as they come

http://www.screwfix.com/p/jg-speedfit-15svp-isolating-valve-15mm/12372

http://www.screwfix.com/p/tube-cutter-3-28mm/49428

 

[Rollerball]

I like that idea, but is there an 'easy fit' type of valve that doesn't involve pipe cutting and soldering?

These are about as easy as you can get - push fit, but you do want a pipe cutter to make it easy so second link is about as basic as they come

http://www.screwfix.com/p/jg-speedfit-15svp-isolating-valve-15mm/12372

http://www.screwfix.com/p/tube-cutter-3-28mm/49428[/QUOTE]

Great, thanks.

Also thought it a good idea (before your reply) to start a thread on this query:

//www.diynot.com/forums/plumbing/isolation-valves-need-some-fitting-advice.388341/#2984541