Any ideas - hot water tank problem

[Ladysaint]

I am posting this again as suggested by Admin.
I have just had my hot water tank changed as the old one kept causing the electrics to trip out due to the build up of lime scale and silt over a 50 year period and it had also started leaking. The hot water tank is in my airing cupboard next door to the bathroom in a position slightly higher than the bath taps so the flow previously was never that great but acceptable. I live in an ex council maisonette and cannot move the tank to an alternative position. I don't have a loft or heating system other than under floor heating and a few electric radiators. The taps are separate taps and the plumber who installed the new tank has been out 4 times now to try and solve the problem and think he has now given up. He is saying that the next step is to completely replumb the bathroom but I have already spent in the region of £1k and not prepared to spend anymore until I know what the problem is.
The cold tap receives mains pressure water directly, so there is no problem with that, while the hot tap receives water under gravity from the tank. When the water in the tank is completely cold it runs at an acceptable level to fill the bath, however when the water is hot it only trickles very slightly through the tap. The hot tap downstairs in the kitchen runs a bit faster and we can live with that.
After installation the plumber thoroughly flushed the whole system out so there was no air present and when he connected the tank fill water main directly to the hot tap pipework to test for blockages there was no pressure loss so he (and we) are at a loss as to why the hot water will not flow through.
How can the same water from a tank flowing under gravity operate perfectly well when the water is cold but not when the water is hot when it takes exactly the same route from the incoming water main?
Any advice or help would be greatly appreciated. Thank you.

 

[SimonG]

Have you changed your bath taps? If you have are they suitable for low pressure?

 

[Ladysaint]

I am happy to change the taps if this helps but cant understand why the water would come out of the taps from the hot water tank when it is cold at an acceptable level but when the water is hot it doesn't. I am willing to do anything as my little boy has to go to family to have a bath and this has been going on for a few weeks now.

 

[SimonG]

So thats a yes then, you have new bath taps as well?

 

[Ladysaint]

Sorry I haven't explained myself very well. I have not replaced the taps on either the sink or bath yet, quite happy to do so if this is what the problem is. The taps worked fine with the old hot water tank and work well when cold water comes out of the hot water tank but not when the water is hot. Appreciate your help and advice Simon.

 

[kris]

Hi there, when the tank was changed did your engineer give you options to what u could do, I E :- like putting in a pressurised hot water tank, ( if certain criteria is met ) , this would've certainly fixed your pressure issues, ?

 

[Ray Stafford]

If I recall the OP's first posting, then nothing has changed, except when the water is hot, it only trickles out. When she runs cold water through the hot system, it runs fine. (at least, that is my understanding).

I suspected that there might be a thermostatic mixer under the bath, but apparently it is affecting both bath and basin.

 

[SimonG]

Right then. Forget the taps.

So far you have spent nearly a thousand pounds on getting a cylinder changed. If thats tru then its a shame as you may have been able to go down the unvented route.

Off the top of my head I cant think what could be the issue other than something that is expanding and constricting the bore of a fitting once the wateris hot.

It may be time to get another pair of eyes onto it.

 

[Dotty]

I vaguely remember someone talking about a practical joke with a tennis ball. Wonder if this is a variation on that.

 

[zzzjim]

How hot is hot water , not almost scalding like a kettle ?

( sounds interesting .. and frustrating )

 

[Chalked]

With your system, the hot water will have always been poor. But, Being an ex council house there might be a mixing valve under the bath. This might need checking (will fail to cold if faulty)
Or when replacing the cylinder a fragment of scale could have gone down the pipe work and blocked so where on the hot pipe work.
Where are you based? Another set of experienced eyes might find the problem straight away.

 

[SJB]

So it only trickles through when the cylinder has warmed up eh..

Possibly a blending valve in the airing cupboard that has failed and or is blocked with a lump of summat.

Weird one tho if no blender, it does read as if there's something expanding when the system is hot and restricting flow

 

[PhoenixServices]

Is it the washers in the taps expanding too much with hot water? Just a stupid thought really.

 

[Sharp Point]

I got called out to a job with exactly the same symptoms, it was some 3/4 flexi tap con to the taps taps, they were kinked and when hot water was run the heat softened them and made them collapse more to the point of cutting off the flow.

Hope that helps

 

[Plumbstar Tom]

is the hot water tank vented properly? When water is heated it creates bubbles. Trace the draw off from your hot water tank for any up hill spots.

Where about are you? Someone could be close to pop in and give a second opinion

 

[mikeyc]

Is there a Surrey flange?

 

[stevetheplumber]

i would remove the tap head while the flow was low see if it improves

 

[Cardiff Plumber]

Send in an image of the cylinder.

 

[lucas121]

What if a bit of the tank insulation fell into the tank when being installed? Would that expand?

 

[JCSPLUMBING]

It has to be the taps or flexible tap connectors if they are used. The hot water draw off cant just slow down when hot as its under the same gravitational force as when its cold. I'm betting there is some plastic pipe or flexi somewhere in the system that's causing this as it's probably kinking as it gets softer. Have you had any leaking joint issues before that's been repaired. It may well of been repaired by a flexi with two compression ends together. I've seen a few of these

 

[JCSPLUMBING]

I am posting this again as suggested by Admin.
I have just had my hot water tank changed as the old one kept causing the electrics to trip out due to the build up of lime scale and silt over a 50 year period and it had also started leaking. The hot water tank is in my airing cupboard next door to the bathroom in a position slightly higher than the bath taps so the flow previously was never that great but acceptable. I live in an ex council maisonette and cannot move the tank to an alternative position. I don't have a loft or heating system other than under floor heating and a few electric radiators. The taps are separate taps and the plumber who installed the new tank has been out 4 times now to try and solve the problem and think he has now given up. He is saying that the next step is to completely replumb the bathroom but I have already spent in the region of £1k and not prepared to spend anymore until I know what the problem is.
The cold tap receives mains pressure water directly, so there is no problem with that, while the hot tap receives water under gravity from the tank. When the water in the tank is completely cold it runs at an acceptable level to fill the bath, however when the water is hot it only trickles very slightly through the tap. The hot tap downstairs in the kitchen runs a bit faster and we can live with that.
After installation the plumber thoroughly flushed the whole system out so there was no air present and when he connected the tank fill water main directly to the hot tap pipework to test for blockages there was no pressure loss so he (and we) are at a loss as to why the hot water will not flow through.
How can the same water from a tank flowing under gravity operate perfectly well when the water is cold but not when the water is hot when it takes exactly the same route from the incoming water main?
Any advice or help would be greatly appreciated. Thank you.

Are you in Southampton? As I see you are a saint?

 

[Ladysaint]

Thanks everyone for all your advice. I am in Southampton JCS Plumbing and what you are suggesting sounds feasible and are you prepared to quote to fix this problem please. Do you give discount to Saints supporters.

 

[Rickster123]

If the problem wasn't happening before you changed the cylinder then I'd imagine some foam lagging has got stuck in a pipe during install.

 

[kozak1968]

Does the bath tap have a flexi on which is bent and restricting the flow? Sorry just got the full post through.

 

[JCSPLUMBING]

Thanks everyone for all your advice. I am in Southampton JCS Plumbing and what you are suggesting sounds feasible and are you prepared to quote to fix this problem please. Do you give discount to Saints supporters.

Haha. I'm sure I can work something out. I'll give you a pm and we can discuss it further.