Difficult pump change

[opps]

A quick search on the web found this wet'n'dry which does have a pump out function (£80).

PondHero Sludge Muncher Vacuum : Pondkeeper is the leading UK pond supplies specialist.

PondHero Sludge Muncher Vacuum Buy pond liners, pond pumps, pond filters and more from Pondkeeper.

www.pondkeeper.co.uk

No idea if it is any good though.

 

[opps]

fanny electrics

???

Sir, this a family friendly forum....

 

[livingstoned]

Still cold.
Every nut is a snag

I hacksawed the pump nuts and removed some pipe to get the pump squeezed through the gap between the cylinder and wall.
The whole area is full of magnetic sludge. The old pump had seized.
The area I've drawn a red box round is so solid I can't even push a skinny 4mm screwdriver through it. Amazing that it worked at all.
I'll have to drill it. Maybe I can use a spring in a drill. Any bright ideas? I did see on here someone using folded curtain wire.
The pipe, once the other side of the wall, is under a bath so not accessible.


There's an illegal gate valve green, which is seized shut now, so I can't empty the F&E pipe easily......
I'm thinking of sticking some citric acid through it, from the F & E cistern . The boiler has a brass plug on it - the sort which is really tight and nothing comes out of the boiler until you ram a screwdriver through the black muck blocking it and get doused in the stuff.. I could get some circulation through it at least.
If I felt good I could chop the vent in the loft and tip some down there too..
It's a bit surprising, I power-flushed the system once when it got slow, after which there was no sign of sludge in the radiators (judging by middle bottom temps and an IR camera). I guess it came back!

Yes I'd love to use a plumber. There are some good ones on here but I don't have details of one who's local and any good. They all retired or died.
No self-respecting plumber would work in the space there is... And there are plenty of the remarkably limited ones.

 

[ChrisJP]

Why is the gate valve on the feed from the F&E tank "illegal"?

 

[livingstoned]

Why is the gate valve on the feed from the F&E tank "illegal"?

I'm not sure what you're asking exactly.
What? A valve in a feed to an open system is proscribed. Probably in the British Standard, in the same place where it's stated you have to have an overheat stat on a sealed system.
Why? Both are anti-meltdown / overheat protections.
What I don't remember actually seeing is the requirement for a combined F/E pipe and Vent pipe to be at least 22mm.

None of those is the issue here, of course!.
It's handy to be able to isolate the supply, until the damned thing fails., I'll replace it with a 1/4 turn full flow valve. They didn't exist when this heating went in.

 

[ChrisJP]

But the system as shown remains open by virtue of the vent pipe curving over the F&E tank and discharging into it, if necessary. The pipe from bottom of the F&E tank doesn't need to be open and a gate or quarter turn valve here is convenient if you want to drain the CH circuit without emptying the F&E tank.

 

[fixitflav]

Yes I know people will be quick to say it shouldn't be like that

And they'd be right! Surprised it's lasted 42 years. There may have been overpumping (flow from the open vent) as the pressure at that point is raised by the cylinder or rads headloss. If you end up doing major changes, worth looking at improving the layout.

 

[livingstoned]

The water supply shouldn't be closable, so it's contrary to the rules.
It doesn't pump over, because the pressure where the feed & expansion pipe joins the loop is higher than where the vent joins. Do you agree??

However, I do have a problem of sludge in the pipes in the airing cupboard. It's thick, it turns a magnetic pick-up tool into a black hedgehog the size of a ping pong ball! It's very difficult to force a thin screwdriver through. I can mechanically remove some of it, but it would block the boiler up if it isn't already. The boiler's a Netaheat so it's a cast iron lump. I have an old flushing pump.
What's the current elixir used to dissolve magnetite? I think it used to be citric acid, and you had to neutralise afterwards with something I forgot.
There was FX-2 I think I remember.
Yes I need a new boiler, but the pipes would have to be cleared then anyway.

 

[ChrisJP]

If the "illegal" gate valve is seized shut, your CH circuit has not been able to receive any water at all from the F&E tank. If you'd had a leak, or needed to drain a radiator, there would be no way to refill the system. Of course, the system remained vented via the pipe curving over the top of the F&E tank.
Do you know when this valve was closed and why this was done?

 

[livingstoned]

If the "illegal" gate valve is seized shut, your CH circuit has not been able to receive any water at all from the F&E tank. I

That's what I said and that's why it's not permitted to have one,
I shut it just recently to work on the pump and it seemed to be letting by so I turned it harder...

Now I have a vertical pipe with a seized valve which is difficult to access, and a head of water above it. Oh well. I may drill up through the brass gate in the valve to let the water through, slowly....



Design errors which contributed to the sludge, are that
1) whenever the pump starts, the level of water in the vent pipe drops by a distance equivalent-ish to the water head drop through the boiler. That means oxygenation and hence the sludge.
2) considering the HW only case, if the resistance through the cylinder were the same as through the boiler, then the water would be brought half the pump head down the vent pipe, so it would be at risk of sucking air.


I could change it, for the limited time it'll exist, to this. (The bypass has always been closed, it can be capped.)
to this, fairly easily. There may be an outbreak of polypipe in the airing cupboard.

I know that having the system under negative pressure, due to the position of the pump, can allegedly cause air ingress through micro-leaks, but I've never heard of or experienced that.

Any suggestion what I/someone can use to dissolve the sludge in the pipes/boiler?? Would X800 do it???

 

[fixitflav]

It doesn't pump over, because the pressure where the feed & expansion pipe joins the loop is higher than where the vent joins. Do you agree?

Just noticed this.
I take back what I said about overpumping - that would be a risk if the cold feed were to the pump suction, not the discharge as you show it.

Possible problem with your arrangement, you could have negative pressure at the pump suction, not ideal as it can suck air in causing corrosion. As an example, if the water level in the F/E tank is 3m above pump suction, boiler Δh 1m, rads Δh 3m - (ignoring pipe loss) pump head = 4m, and pressure at suction minus 1m. Of course your figures will be different.

 

[livingstoned]

Just noticed this.

I added it later! You made me think anyway, at which point I worked out the water level change problem which I'm not sure I thought about before.
Yes as above with a 6m pump, if the boiler resistance is equal to the HW cyl resistance the vent would be 3m below the feed. The inlet to the pump is well below atmospheric.

as it can suck air in causing corrosion.

Indeed - micro leaks, , also in the post above yours!

The level problem can be resolved as I showed, I think, but not much plumbing can be changed because of the access problems, That room really is full, we've been collecting stuff for a long time.

The obvious problem now is sludge. I've undone all the nuts and shoved a magnetic pick up tool as far as I can. It won't go down one 22mm, and from the others it attracts a 4cm plug of magnetite (I assume) flakes each time..

In the back of the garden shed there's a flusher I only used about twice.. If it works I'll try to circulate some chemical, but I'm not sure what would do the job.
This is off the topic of this thread so I'll do a new one