Replacement pump recommendation

[jfb]

On 24/01/2026 at 21:15, Nickfromwales said:

This one may suit your needs and should be available locally LINK

 

[Nickfromwales]

Try again, lol.

[jfb]

9 hours ago, marshian said:

If it's air locked there opening a drain under the boiler

Do you mean a drain point on a low radiator?

[Nickfromwales]

35 minutes ago, jfb said:

Do you mean a drain point on a low radiator?

Most boilers have a drains off point at the underside of the boiler. Not all, but the majority. 
 

You can connect a hose to this, poke the other end down a drain, and open the drain off to pull water and air down / through / out of the hose.

 

You do this with the system on and running btw.

 

Can you have a look for a drain on the boiler? Dont mistakenly open the combustion chamber looking for it though(!) just look under it or take the white metal case off at most. If you don’t see it then, you don’t have one. 

[jfb]

There is very little pipe work to see. Gas enters from the bottoms and flow and return on top.

 

 

[Nickfromwales]

12 hours ago, jfb said:

Boiler probably replaced 10 years ago, old leaky rads replaced for new less than two years ago, no real issue since last week

This says single component failure then, not a build up of air stopping the show.

 

One sensible ‘upgrade’ would be to have a manual air vent (thumb turn type) to vent the pipework atop the boiler, but I honestly doubt there’s a lifelong issue there if it’s run fine for a decade, plus then another 2 years after the rad swap.

[jfb]

21 minutes ago, Nickfromwales said:

This says single component failure then, not a build up of air stopping the show.

Thanks for the replies Nick.

so you don’t think there is anything obviously structurally wrong with the pipe work?

 

[jfb]

One more question for anyone.

 

when you bleed a non automatic pump you do it until you get water coming through.

when I used the auto bleed function on the wilo I didn’t at any point have water come out and the bleeding then stop. Should there be water coming out at the point it successfully bleeds all the air out ?

[Nickfromwales]

1 hour ago, jfb said:

One more question for anyone.

 

when you bleed a non automatic pump you do it until you get water coming through.

when I used the auto bleed function on the wilo I didn’t at any point have water come out and the bleeding then stop. Should there be water coming out at the point it successfully bleeds all the air out ?

Ok. The auto bleed function on a pump is usually just it pulsing / stop-starting to ‘bump’ air around and out of the water circuit.

 

To clarify, an automatic air vent is a piece of equipment that’s installed at the highest point of each circuit, which allows air to be released in your absence.

 

Air comes out, and they they do a little ‘spit’ and then no more water comes out. 
 

When you auto-bled the pump, what exactly did you do? 

[jfb]

14 minutes ago, Nickfromwales said:

When you auto-bled the pump, what exactly did you do? 

Clicked the button on the wilo. It made some different sounds for the duration (the display said it was doing the auto bleed). Eventually I stopped it after 15 minutes. Did it a couple times.

 

no automatic air vents on the system as far as I know

Edited 3 hours ago by jfb

[Nickfromwales]

2 minutes ago, jfb said:

Clicked the button on the wilo. It made some different sounds for the duration (the display said it was doing the auto bleed). Eventually I stopped it after 15 minutes. Did it a couple times.

 

no automatic air vents on the system as far as I know

Ok, then the rads upstairs must be where the system shunts air to, and then you bleed these off. That suggests the pump and valves etc are all lower than the first floor rads, and therefore you may not need an auto air vent in the system.

[jfb]

7 minutes ago, Nickfromwales said:

Ok, then the rads upstairs must be where the system shunts air to, and then you bleed these off. That suggests the pump and valves etc are all lower than the first floor rads, and therefore you may not need an auto air vent in the system.

The pump is in the hot water cupboard upstairs and I’m pretty sure it is higher than the bleed point on the rads.  

[Nickfromwales]

On 24/01/2026 at 22:03, ProDave said:

First check the header tank is not dry.

Another big issue with gravity arrangements is that the T blocks up with crud where the F&E (small plastic “Feed and Expansion” tank in the attic) T’s into the heating system. This prevents the feed water topping the system back up, but the tank stays full and you don’t think there’s an issue with it filling itself up ‘automatically’.

 

Every single time I did “old to new” conversions, someone was tasked with popping as many floorboards as was necessary to find the T in question, and every single one got cut out, and replaced with a straight section of new pipe (lazy plumbers just cap the 15mm pipe off and bin the F&E tank ( @SimonD will know what state these get into ). 
 

The F&E tank can be full to look at, but be sat there not actually feeding back into the system, so the entire first floor of rads would often be less than half full of water and doing diddly-squat as no new ‘feed’ water getting into the system as needed. It doesn’t take much of a blockage to stop this. 

 

Seeing as this thread was just moving sideways, the next thing to do is reverse fill the system and then I think we’ll get some results. As the system refuses to get itself going after the pump change, and the topology makes me think it should, then this is what I think is going on.

 

@jfb, you will need to get a hose on an outside tap and bring it inside.

 

Q: can you find a drain off cock down as low in the system as possible. 

 

 

 

Let us see a pic of the pumps and motorised valves etc, wide angled if possible so we can see the pipework etc, and under the pump or near one of the downstairs rads is where you should find a drain off.

 

You need a +1 and a +2 ideally for the reverse full up btw, so bribe a mate with beer and send them up the attic with a torch. They need to monitor that tank without deviation. 

 

Put the hose onto the drain off and use a suitably sized jubilee / hose clip to secure it on tight as feck. You do not want this coming off ‘mid whoosh’, ask me how I first found this out……

 

So. Once the hose is on, and you’ve secured it, and it’s connected to the outside tap (or a mains cold washing machine tap) you now have the mother of all balancing acts to perform.

 

You will need to open the outside tap just a half turn or so, so you can see the hose filling with water pressure. It’s not advisable to let this fully equalise with the cold mains as that’s when the hose and clip are going to want to shoot off.

 

The idea is to get this to have more ‘head’ / pressure than the heating system. This is usually noted when the hose on the drain off starts to swell up and start to look like it is about to go pop.
 

Then you open the drain off cock and let cold mains enter the system from the bottom up. 
 

Now the fun begins.

 

Have the heating turned on and running, so the motorised valve is energised and open, and the pump is running on its highest setting.

 

You then need to have the attic victim on high alert. You will be back filling the system so the thing to go wrong here is to be filling up the system unaware that the F&E tank is now about to overflow and puke out into the attic.
 

This balancing act is controlled by attic person and hose / outside tap person being on their phones all the way through this purge process, so the moment the F&E tank starts to fill up, the person on the outside tap can speed up or slow down to stop the F&E tank overflowing. It’s fine for the water to get up to the overflow and some escape down it, but this needs to be”live communications” for obvs reasons. If it gets to the overflow, tap person shuts off the cold mains and stands by.
 

Now rope the wife in.

 

Whilst this is going on, you need to vent the rads on the first floor and see if they start letting air out.
 

If the F&E tank T is blocked, then you may not see the water level begin to rise in the tank immediately, so be prepared for that to go pop all of a sudden (as the crud gives way) and then tap person needs to be told to slow down or stop with a bit of gusto.
 

Once rads are confirmed as full of water, and the F&E tank has raised / lowered at least once, then you turn off the outside tap, close the drain off, and go see if all is now working as it should.

 

If this doesn’t get the system working, I will eat everybody’s hats.

 

Issues to avoid: 

Blasting cold mains water clean out of the F&E tank. Please video this for our entertainment if so. 
 

Letting the central heating water get down the hose and back into the cold mains pipe work via the outside tap. Likelihood is that the cold mains pressure will mean this cannot happen, but one to consider. 
 

When you’ve finished doing this purge, run lots of clean water through the hose to make sure it’s not contaminated, eg with inhibitor etc.

 

After a day or two of normal operation, you can look at treating with inhibitor and booking a holiday. 

 

Hows that sound? One for today and then you’ll be up and running I reckon. 

[Nickfromwales]

1 hour ago, jfb said:

The pump is in the hot water cupboard upstairs and I’m pretty sure it is higher than the bleed point on the rads.  

There should be at least a manual air bleed then? How hard have you hunted for one? 
 

[marshian]

22 minutes ago, Nickfromwales said:

Another big issue with gravity arrangements is that the T blocks up with crud where the F&E (small plastic “Feed and Expansion” tank in the attic) T’s into the heating system. This prevents the feed water topping the system back up, but the tank stays full and you don’t think there’s an issue with it filling itself up ‘automatically’.

 

Every single time I did “old to new” conversions, someone was tasked with popping as many floorboards as was necessary to find the T in question, and every single one got cut out, and replaced with a straight section of new pipe (lazy plumbers just cap the 15mm pipe off and bin the F&E tank ( @SimonD will know what state these get into ). 
 

The F&E tank can be full to look at, but be sat there not actually feeding back into the system, so the entire first floor of rads would often be less than half full of water and doing diddly-squat as no new ‘feed’ water getting into the system as needed. It doesn’t take much of a blockage to stop this. 

 

Seeing as this thread was just moving sideways, the next thing to do is reverse fill the system and then I think we’ll get some results. As the system refuses to get itself going after the pump change, and the topology makes me think it should, then this is what I think is going on.

 

@jfb, you will need to get a hose on an outside tap and bring it inside.

 

Q: can you find a drain off cock down as low in the system as possible. 

 

 

 

Let us see a pic of the pumps and motorised valves etc, wide angled if possible so we can see the pipework etc, and under the pump or near one of the downstairs rads is where you should find a drain off.

 

You need a +1 and a +2 ideally for the reverse full up btw, so bribe a mate with beer and send them up the attic with a torch. They need to monitor that tank without deviation. 

 

Put the hose onto the drain off and use a suitably sized jubilee / hose clip to secure it on tight as feck. You do not want this coming off ‘mid whoosh’, ask me how I first found this out……

 

So. Once the hose is on, and you’ve secured it, and it’s connected to the outside tap (or a mains cold washing machine tap) you now have the mother of all balancing acts to perform.

 

You will need to open the outside tap just a half turn or so, so you can see the hose filling with water pressure. It’s not advisable to let this fully equalise with the cold mains as that’s when the hose and clip are going to want to shoot off.

 

The idea is to get this to have more ‘head’ / pressure than the heating system. This is usually noted when the hose on the drain off starts to swell up and start to look like it is about to go pop.
 

Then you open the drain off cock and let cold mains enter the system from the bottom up. 
 

Now the fun begins.

 

Have the heating turned on and running, so the motorised valve is energised and open, and the pump is running on its highest setting.

 

You then need to have the attic victim on high alert. You will be back filling the system so the thing to go wrong here is to be filling up the system unaware that the F&E tank is now about to overflow and puke out into the attic.
 

This balancing act is controlled by attic person and hose / outside tap person being on their phones all the way through this purge process, so the moment the F&E tank starts to fill up, the person on the outside tap can speed up or slow down to stop the F&E tank overflowing. It’s fine for the water to get up to the overflow and some escape down it, but this needs to be”live communications” for obvs reasons. If it gets to the overflow, tap person shuts off the cold mains and stands by.
 

Now rope the wife in.

 

Whilst this is going on, you need to vent the rads on the first floor and see if they start letting air out.
 

If the F&E tank T is blocked, then you may not see the water level begin to rise in the tank immediately, so be prepared for that to go pop all of a sudden (as the crud gives way) and then tap person needs to be told to slow down or stop with a bit of gusto.
 

Once rads are confirmed as full of water, and the F&E tank has raised / lowered at least once, then you turn off the outside tap, close the drain off, and go see if all is now working as it should.

 

If this doesn’t get the system working, I will eat everybody’s hats.

 

Issues to avoid: 

Blasting cold mains water clean out of the F&E tank. Please video this for our entertainment if so. 
 

Letting the central heating water get down the hose and back into the cold mains pipe work via the outside tap. Likelihood is that the cold mains pressure will mean this cannot happen, but one to consider. 
 

When you’ve finished doing this purge, run lots of clean water through the hose to make sure it’s not contaminated, eg with inhibitor etc.

 

After a day or two of normal operation, you can look at treating with inhibitor and booking a holiday. 

 

Hows that sound? One for today and then you’ll be up and running I reckon. 

 

I had to do this a few years back when I air locked the boiler - it works quite well

 

But if you aren't prepared with people at F&E tank and any bleed points it can get a bit damp

[SimonD]

36 minutes ago, Nickfromwales said:

Every single time I did “old to new” conversions, someone was tasked with popping as many floorboards as was necessary to find the T in question, and every single one got cut out, and replaced with a straight section of new pipe (lazy plumbers just cap the 15mm pipe off and bin the F&E tank ( @SimonD will know what state these get into ). 

 

Oh yes, and one of the reasons I avoid heat only installs like the plague. The last one I did, after being sweet talked by the owner, I filled up the system about 10am in the morning but didn't get out of there until 17.30. She was flapping saying it was supposed to be a simple install and I reminded her she hadn't touched the system in 22 years and this was why the water was black when I fushed all the rads. And some of those capped off Tees just collect a nice little air bubble and you've got a nearly unclearable air lock.

[marshian]

Good trick for pinch points for vented systems is to put a magnet against the copper pipework - if it sticks to the pipe then you've got a magnetite build up - how much you can't tell but you've definitely got an issue in that location

[Nickfromwales]

4 minutes ago, marshian said:

Good trick for pinch points for vented systems is to put a magnet against the copper pipework - if it sticks to the pipe then you've got a magnetite build up - how much you can't tell but you've definitely got an issue in that location

Yup. 👍. 
 

 

23 minutes ago, SimonD said:

 

Oh yes, and one of the reasons I avoid heat only installs like the plague. The last one I did, after being sweet talked by the owner, I filled up the system about 10am in the morning but didn't get out of there until 17.30. She was flapping saying it was supposed to be a simple install and I reminded her she hadn't touched the system in 22 years and this was why the water was black when I fushed all the rads. And some of those capped off Tees just collect a nice little air bubble and you've got a nearly unclearable air lock.

We used to keep the worst ones, usually those off coal setups, where you literally can’t see through a 6” piece of pipe with the T in the middle of it.

 

It was hard work to get a screwdriver through some of them.

 

Heat only systems suck imho, and its system boiler / sealed and pressurised all the way these days.

 

Just done a big job for another member here, and their brand new WB heat only boiler was a total PITA to purge and get going again. The only thing I didn’t touch was the biggest arse to sort out when recommissioning the UVC and heating etc.

 

All the components (pumps / differential bypass / motorised vales / expansion vessel and top up loop etc) strewn throughout the locality up the attic….just WHY?!?! when a system boiler conversion would have been a doddle and deleted most of that     
 

6m of gas pipe, and one lonely (broken) clip was their offering to secure said gas pipe. The only thing otherwise securing the gas run was the nut and olive on the jig of the boiler 😮. Embarrassingly shite work. All sorted now thank feck. 
 

I love attics, me. 

[Nickfromwales]

@jfb

 

May be a good idea to add a TF1 mag filter.