Hot water pump intermittent

[Alexalee]

I have a pump for my hot water system.
Tonight it's being very intermittent and the flow goes from slow to very slow... if I turn another hot tap on at the same time absolutely nothing comes out.
New pump or blockage?

or it might be the supply. Has any air come out of the taps? What are the cold taps running like?

Is it pumping the hot water out of a cylinder? What colour?

some photos of your installation may give more clues.

Hi yes out of a blue cylinder
No air
Cold taps are fine
Thanks

have a look at the cold water tank in the loft. Is it full?

I will have a look tommorrow.
What would make you suspect the cold tank?
Thanks again pigletjohn

the pump can only suck as much hot water from the cylinder as flows into it from the cold loft tank. It cannot create a vacuum (though it can create an air bubble)

the loft tank might be low on water (or perhaps it had already been used up by a longbath or shower) or it might have a drowned pigeon or something blocking the pipe.

if there is plenty of water in the loft tank, and it is flowing freely into the cylinder, then any hot taps that are not fed from the pump would be flowing freely.

Cold water tank is full
Could there be a blockage in the hot water cylinder?

Unlikely

Are you in a flat or a house?

How far above ground level is the cold tank?

And the hot cylinder?

And the pump?

And the bathroom?

Is every hot tap in your home pumped?

Why?

If it's anything like our pump, it will have a filter. It may have crud in the filter and need a clean out. We had trouble with ours when it was first installed due to some quite small bits of stuff that blocked it. (Long and boring story, but we had to empty and hoover out the cold water tank eventually. That did the trick.)

Hmm
House
Cold tank on 2nd floor
Hot cylinder on 1st floor
Pump right next to cylinder
2 bathrooms on first floor, 1 on gf with kitchen
Yes the pump does all the water
No idea why... I assume we had weak hot pressure. Cold pressure is high though a 12 litres per minute

I expect the cold water comes straight off the mains. Common practice in some towns.

What colour is your pump? Not yellow, is it? Does it appear to hum softly when running? Picture, please

From what you describe I see no reason to pump the hot water, except for a shower. It would be simpler and quieter to let everything else run on gravity. If flow is poor there must be a defect such as bad pipe layout or constricting valves. If you end up needing a pump, consider getting a pump for the shower only, or a shower incorporating a pump, and bridging the pipework at your old shower position.

Good idea to check the pump filters (if any) although any dirt would usually collect at the bottom of the cylinder and not reach the pump. Apart from fragments of drowned wildlife, you might find limescale flakes if you are in a hard water area (they will also be visible at the bottom of the loft tank).

See if you can get a garden hosepipe conector that will fit on the pipe supplying water to the pump, and see what the flow is like unpumped. It is very likely 3/4" BSP (the same size as a washing machine hose, and you can buy them in various lengths)

Also look at any flexible hose connectors to see if they are twisted or kinked, and at all the service valves to ensure they are not closed, including in the loft and around the pump. Post some pics of the installation please.

Hi
Cant get to photo the pump easily, but it isnt yellow, I think it was a salamander pump, but in about 5 years ago
It only seems to happen when the main bath hot tap has been run, then subsequently buggers up the rest of the hot taps for a few minutes, then they seem to work fine again.
The tank in the loft is very small... probably only about 10 litres, but no blockage in there
The pump is very inaccessible but sounds like I might need dh to have a look at the filters if there are any
But as it's mainly caused by 1 tap I'd it more likely to be air related?

"It only seems to happen when the main bath hot tap has been run, then subsequently buggers up the rest of the hot taps for a few minutes, then they seem to work fine again."

that would fit if the tank had been drained. There would be no more water available until it filled up again.

10 litres sounds very small, verging on the impossible. Are you sure there isn't another tank somewhere? A small tank is usually expansion and feed for the radiators, not for the taps.

Some cylinders have a round tank for cold wate on the top. You'll see a sort of "waist" where they join, and they have a lid that can be removed for access to repair the ballcock. This type is likely to have very poor pressure. The top looks flat, not domed (see pic)

Photos will help a lot.

Pigletjohn thank you for all your advice... you really are a godsend on this site

An update
Hubby got home this afternoon and decided to go and investigate the pump... took the inlet hose off and could see it was all furred up... took it off to try and clean as he couldn't find a new one in the screwfix catalogue. It was 90% furred up and the 10% left in the middle you could see some loose blue debris . So he cut the filter out and it is now twice as powerful as it's ever been and 10 times better than it was before.
I assume the pump will now fur up alot sooner and will need replacing quicker but i am just happy I can have a bath again
Thanks again