Slow hot water after fitting new immersion tank

[Losingthewilltolive]

Can someone please tell me what I have done wrong. Fitted a new tank exactly as old one recently but since then the hot water pressure up and downstairs has been really low. (E.g. A good 10/15 mins to fill kitchen sink) It is a gravity fed system. No gas. So far tried to clear any airlocks, fitted new valve, flushed all pipes to taps, checked tank in loft. No clue what to do next. Old tank had good hot water pressure so this is a new problem. Thanks in advance for any advice. Should add all 22mm pushfit. No flexi pipe

 

[Chuck]

My guess is there a gate valve between the cold water store in the roof and the inlet to your tank that was shut when the new cylinder was fitted. It did not open fully again on completion of the work. Sometimes the spindle comes away from the gate so it turns but the valve stays closed.

Be careful that you don't collapse your new tank by drawing off water with the inlet blocked.

 

[Losingthewilltolive]

My guess is there a gate valve between the cold water store in the roof and the inlet to your tank that was shut when the new cylinder was fitted. It did not open fully again on completion of the work. Sometimes the spindle comes away from the gate so it turns but the valve stays closed.

Be careful that you don't collapse your new tank by drawing off water with the inlet blocked.

Thanks for the quick response. That’s the valve I changed and it made no difference

 

[townfanjon]

It may be the pic but put a spirit level on the top of the pipe leaving the cylinder it looks like it falls down , it should go slightly up .

 

[John.g]

A long shot, is there any possibility that the hot water take off is extending down into the cylinder possibly causing a air lock in the top.

 

[Aire]

Could be an airlock, could also be debris in the hot water outlet, had it a few times where I've been sent to new installs with poor flow only to find a bit of the foam insulation has fallen into the tank then parially blocked the outlet when filled up.

 

[Burger]

Check the pipe on cold feed from first elbow to 2nd, looks like it’s raised slightly, could be causing an issue.

 

[Darren Jackson]

The horizontal section of the cold feed looks like it has a slight rise in it instead of a slight fall to the cylinder. And then the opposite on the hot water draw off, it should have a slight rise away from the cylinder not dead level or a fall on it. Both could trap air and restrict the flow.

 

[Losingthewilltolive]

It may be the pic but put a spirit level on the top of the pipe leaving the cylinder it looks like it falls down , it should go slightly up .

It would seem my photography skills are as lacking as my plumbing abilities. The pipe does run slightly up. But thanks for your response.
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The horizontal section of the cold feed looks like it has a slight rise in it instead of a slight fall to the cylinder. And then the opposite on the hot water draw off, it should have a slight rise away from the cylinder not dead level or a fall on it. Both could trap air and restrict the flow.

Thank you. The outlet is slightly upwards but my camera angle does suggest otherwise. The cold inlet though is slightly higher so I will rectify that later. Thank you
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Check the pipe on cold feed from first elbow to 2nd, looks like it’s raised slightly, could be causing an issue.

Thanks, will rectify it later
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Could be an airlock, could also be debris in the hot water outlet, had it a few times where I've been sent to new installs with poor flow only to find a bit of the foam insulation has fallen into the tank then parially blocked the outlet when filled up.

Thanks for this. I think you are on to something here. When I took the end off the kitchen tap a tiny bit of what appeared to be foam fell out. Didn’t twig at the time. Will need to flush the pipe in to something to make sure it’s not blocked.

 

[king of pipes]

Also check the CWST outlet is not obstructed any valves are fully open or any red handled gate valves are not snapped off half shut . Kop

 

[Losingthewilltolive]

Could be an airlock, could also be debris in the hot water outlet, had it a few times where I've been sent to new installs with poor flow only to find a bit of the foam insulation has fallen into the tank then parially blocked the outlet when filled up.

Thanks for this. I think you are on to something here. When I took the end off the kitchen tap a tiny bit of what appeared to be foam fell out. Didn’t twig at the time. Will need to flush the pipe in to something to make sure it’s not blocked.

Also check the CWST outlet is not obstructed any valves are fully open or any red handled gate valves are not snapped off half shut . Kop

Thanks, will do

 

[Scott_D]

PTFE tape blocking the cold feed?

 

[Losingthewilltolive]

Ok, so I have moved the cold water inlet pipe, flushed through all the pipes and there are definitely no blockages as it runs out fast but still no hot water pressure when I fill up the tank again.
Could it be the overflow pipe that goes back up to the loft tank that is causing the immersion tank to lose pressure? Could it be I am not filling the tank back up correctly and I am causing air locks every time? Is there a certain routine I should follow to fill it back up? Would moving the overflow so it goes in the side of the loft tank (under water level) or should it always go up and over the top of the tank? Really wish I could afford a plumber to help with this but I only get a small pension
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PTFE tape blocking the cold feed?

Checked and not an issue. Thanks for the suggestion though

 

[Burger]

Did you undo and check for foam at the top of hot outlet as Craig suggested? If you have some spare push fit elbows you could try terminating some parts into a bucket to try and eliminate the issue?

 

[Losingthewilltolive]

Did you undo and check for foam at the top of hot outlet as Craig suggested? If you have some spare push fit elbows you could try terminating some parts into a bucket to try and eliminate the issue?

Yes we tried that and the tank is clean. I am now thinking it has to be an air lock issue as the kitchen and bathroom basin is now running ok but the bath is still very slow but I don’t know how the airlocks get in when I am filling up. The two taps only started running better after I blocked off the overflow pipe to see if it added more pressure

 

[Burger]

Yes we tried that and the tank is clean. I am now thinking it has to be an air lock issue as the kitchen and bathroom basin is now running ok but the bath is still very slow but I don’t know how the airlocks get in when I am filling up. The two taps only started running better after I blocked off the overflow pipe to see if it added more pressure

The "overflow" which you refer to is the vent and expansion pipe. Try blasting mains water from cold through the hot - usually the washing machine fill valves.

 

[Leeb1987]

You need to be logical about your fault finding step by step an you will narrow it down pretty quick. 1, Do you have good pressure into tank? Shut off and Disconnect tank inlet, terminate in to a bucket and turn on, good pressure? Have a look into the inlet make sure there’s nothing restricting inlet at tank connector. 2, disconnect tank outlet and terminate in to bucket, does it have good pressure? Look in outlet and make sure no restrictions. If it has good pressure from tank but not from taps then it’s going to be either a bad airlock or a gate valve u/s after the tank outlet maybe? Open all hot taps and connect cold to hot at washing machine connectors and turn on off a few times. If it has poor pressure then it will probably be pipe too far in tank causing airlock or restriction in tank
Hth

 

[Aire]

Have you only changed the tank? Or is the install part of a larger job where you've also changed kitchen and bathroom taps etc?

 

[Burger]

One thing that hasn’t been mentioned, is the float valve filling ok and the cold tank full?

 

[Chuck]

Yes we tried that and the tank is clean. I am now thinking it has to be an air lock issue as the kitchen and bathroom basin is now running ok but the bath is still very slow but I don’t know how the airlocks get in when I am filling up. The two taps only started running better after I blocked off the overflow pipe to see if it added more pressure

Make sure that you have 'unblocked off the overflow pipe'. It's not an overflow pipe, it is there to allow expansion and hence prevent the tank exploding.

It seems possible to me that whatever was previously blocking the outlet of the tank (foam packing?) has been pushed through the pipework by your early attempts and is now lodged somewhere between the point that the kitchen and bathroom feeds branch off and the bath taps.

 

[John.g]

If there is free flow from the top of the cylinder checked/proven by means of a short length of pipe as was suggested above and if there has been no change to the pipework etc then surely it points to some blockage or air lock in the downstream piping?

 

[Losingthewilltolive]

Thank you everyone for your advice. You have all been a great help. Restoring a good water flow to the kitchen was the main thing I needed to do. We shall just have to live with the slow bath feed. We flushed all sections of the pipes with cold water and there was a good flow of water to each tap. We also checked the tank in the loft and the pipe leading to the immersion tank which also had a good flow rate.

 

[Leeb1987]

Thank you everyone for your advice. You have all been a great help. Restoring a good water flow to the kitchen was the main thing I needed to do. We shall just have to live with the slow bath feed. We flushed all sections of the pipes with cold water and there was a good flow of water to each tap. We also checked the tank in the loft and the pipe leading to the immersion tank which also had a good flow rate.

Sounds like there’s debris/airlock in the bathroom still

 

[Losingthewilltolive]

Sounds like there’s debris/airlock in the bathroom still

Yeah, it has to be air as the cold water flush had all of the hot water taps running really well. I just don’t know how to clear it or what I am doing wrong to get airlocks in the first place