Hot water fails to continue to arrive...

[Bill]

In message , bert writes

Cue my favourite, long, story about fathers blockage.

Briefly a rat had died in the storage tank and eventually its' remains had tried to flow down the outlet pipe, partially blocking it. The complaint was of low water flow from the bathroom taps. When he pulled the "piece of string" that he could see in the bottom of the tank from the outlet pipe most of the rat came back out again.

Moral of the story is to keep the lid of the tank well sealed, but not air tight.

I hope your problem is less yucky.

[Maurice]

- but now, after running hot water, when a HW tap is then turned off there is a grinding/rumbling noise from the pump for 5 seconds or so. (Not heard before)

So perhaps the earlier problem was due to impending HW impeller failure (or it has been damaged by the earlier failure).

Awaiting response from installer (as pump still under warranty)...

[Maurice]

The though did occur to me that the HW feed from the tank might be partially blocked, though I couuld't see how that would explain the symptoms (starting with good flow, then dwindling; turn tap off then on again: same thing. I would have though it would be just a steady dribble.

[Tim+]

Could just be cavitating due to partial blockage of supply to HW cylinder. You need to look in your header tank for foreign bodies and check to see if you've got any steel pipework between your header tank and your HW cylinder.

Tim

[Tim+]

Well that sounds like a classic air-lock but if your water has started working again, that should have cleared.

Have you tried back flushing from mains pressure cold into a hot tap? (Do make sure not to back flush too much or at least make sure that your header tank has a working overflow - you don't want to flood your loft!).

Tim

[Maurice]

Yes - it appeared not to work, but later got some air out of upstairs tap and the system was back to normal - apart from the

5-second rumble after turning off a HW tap.

This pump is silent when pumping, whether hot or cold. It's only after the recent episode that the after-turn-off 5 seconds of rumble can be heard, and only after pumping HW. Perhaps it always did it and I hadn't noticed, but why only after HW? Ominously the guy who fitted the replacement in August (previous owner) said that the pump had burned out then. The same guy has confirmed that the pump is still under warranty, but has added: "If you did have an airlock and the pump was running without water that would destroy it fairly quickly. Unfortunately the manufacturers warranty would not cover this" Is that general with such pumps - they cannot detect air and shut off? (I had assumed that's what this one was doing, when HW delivery kept tailing off.)

[Tricky Dicky]

We used to get air locks in the feed pipe from the CW tank and the HW cylin der if either was drained down, I think partly due to a section of pipe in the loft running very horizontally for a couple of metres. Back flushing wa s the answer simply done at the hot and cold feeds for the washing machine. Bit more of a problem to do if you only have a cold feed like many modern washers.

Richard