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Discuss Heat Only Boiler - Radiators Hot But No Hot Water in the Central Heating Forum area at PlumbersForums.net

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11
Hi Guys,
I have a heat only boiler with two tanks in the loft. I have recently drained the system and since then i am not getting any hot water. The hot water tank front two pipes are hot, however the one coming out the top is cold.

Radiators are heating up completely fine.

Hot water taps there doesn't appear to be much pressure, i have tried the covering the outlet on a mixer tap and turning on to remove any airlocks (how long should i keep taps on for as i can hear water moving while i am doing it), but still no joy.

Any help really appreciated

Thanks
 

Undertrained

Plumber
Gas Engineer
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758
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1
Good evening Joel,

For the pressure, check the cold water storage cistern in the loft that feeds the hot water cylinder - make sure there’s water in it. By no hot water, I’m reading it as water comes out of the tap, but isn’t hot? - if so, do you know what motorised valves you have?
 
Messages
11
Good evening Joel,

For the pressure, check the cold water storage cistern in the loft that feeds the hot water cylinder - make sure there’s water in it. By no hot water, I’m reading it as water comes out of the tap, but isn’t hot? - if so, do you know what motorised valves you have?
Hey Thanks for the quick response. Yeah water tank in the loft is full up and i do get free flowing water out of all hot water taps, although not much pressure. Sorry i dont know what you mean by motorised valves.
I have also notice two radiators also will not heat up (one of the two in the living room and the one in the bedroom above)
 
Messages
11
Can you take a photo of the airing cupboard? (Re: valves). The rads not heating are they bled of water?
Sorry not at the only property so the attached photo is the only one i have (sorry for the owners boxers haha). The rads not heating do have water (water comes out when i bleed at the top) the pipes entering the radiator from the floor are also cold.

Thanks again for all your help
 

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Undertrained

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Gas Engineer
Messages
758
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1
Unfortunately the photo doesn’t tell me what zone valve(s) there is. You’re looking for the following:

One of these (or similar):

1630271070090.jpeg

Or two of these (or similar):

1630271106148.jpeg

The rads not heating will probably be trapped air somewhere or a balancing issue.
 
Messages
11
Unfortunately the photo doesn’t tell me what zone valve(s) there is. You’re looking for the following:

One of these (or similar):

View attachment 63244

Or two of these (or similar):

View attachment 63245

The rads not heating will probably be trapped air somewhere or a balancing issue.
It has one of those below the 3 way connector (one pipe leading to the tank, one to the like a bleed valve and then one going down to that valve) All those pipes are hot and water comes out the bleed screw at the top.

The pipe coming out the top of the actual tank however is the only one that is cold.
 
Messages
11
Daft question, but have you given it time to heat up? Was the pump bled?
Not a daft question :) I have never had a system like this, always a combi boiler so not sure on its functionality. Left it on for about 1.5 hours? Strangely i slid control over to turn just the hot water on initially but the radiators heated up; in the end i turned both on.

I have not bled the pump, didnt know that was needed.
 

Undertrained

Plumber
Gas Engineer
Messages
758
Solutions
1
The pipes going in and out of the pump were hot though but can still bleed if you think worthwhile?
Might be worth a shot as there may be a little air trapped. Undo the big screw in the middle, and be prepared for a little water escaping, so a small container or old towel or both. Do this until any air is released.

1.5 hours should be enough. If the rads heated up with the hot water on, then the valve motor might be sticking.
 
Messages
11
Might be worth a shot as there may be a little air trapped. Undo the big screw in the middle, and be prepared for a little water escaping, so a small container or old towel or both. Do this until any air is released.
Brill i will give that a go tomorrow :)
sorry last question, when trying the cover the mixer tap to forces water back in the hot pipes, how long should i do that for and is it best to use an upstairs or downstairs tap?
 

Undertrained

Plumber
Gas Engineer
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758
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1
It needs to be done until there is sufficient flow from the taps and removing air. Sometimes it’s best at 2 washing machine valves if available. Doesn’t matter which tap.
 
Messages
11
It needs to be done until there is sufficient flow from the taps and removing air. Sometimes it’s best at 2 washing machine valves if available. Doesn’t matter which tap.
Brill, will give it another go as i could hear the water flowing through the pipes so maybe leave it flowing longer. Thanks again for all your help, really appreciate it
 

ShaunCorbs

Staff member
S. Mod
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It won’t be the same pressure as your used to as it’s gravity so will be a lot lower this is normal

Have you tried sliding the other slider across as you will have 3 the bottom one is your hot water set this to constant for now and test the water out of the tap in an hour or so
 
J

Joelp899

It won’t be the same pressure as your used to as it’s gravity so will be a lot lower this is normal

Have you tried sliding the other slider across as you will have 3 the bottom one is your hot water set this to constant for now and test the water out of the tap in an hour or so
Hey thanks for the response. Yeah I slid both heating and water across (top one is just timer), I set them to once? I will try constant tomorrow and see if that makes a difference
 
Messages
11

Hey what was edited? I am at the property now and tried releasing any air in the pump but just weeps water instantly, tried both switches on constant and still no hot water and similar weak pressure. I have attached a better picture which may be easier to see.
I'm currently trying to heat using the immersion but as before the bottom two pipes are very hot but the one coming out the top stone cold!
Think my next thing is to fully drain full system and start again?
 

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Undertrained

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Just something I put that wasn’t relevant. Anyway, the pipe going into the cylinder from the 3 pot valve is that hot?
 
Messages
11
Just something I put that wasn’t relevant. Anyway, the pipe going into the cylinder from the 3 pot valve is that hot?

We have hot water!!!!!! No idea how or why I turned the immersion on, every outlet turned on full, didn't see or notice any spluttering from the pipe, then did the mixer tap trick with everything open
View attachment PXL_20210830_130813957.mp4
View attachment PXL_20210830_130949444.mp4
but then sudden warm water!!! However the tank is now very noisy? Attached a video.

The water pressure is also very poor but I'm not sure if that is due to more air locks or just the norm for a gravity fed system.

Thanks again for your patience and help
 

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