Taking forever to pressurise central heating system. Why is this so?

[siliconeseal]

@BlueLoo Please continue going out on such limbs! I'm calling it a night as far as loft expeditions are concerned. Last thing I need is to fall down between the floor-boards a couple of hours from midnight. But tomorrow is another day and I'll definitely trace the pipe.

 

[Harry Bloomfield]

Thank you Harry. I too was wondering what could be changing in the pipe over the past 3-4 years, given that its lying undisturbed in the loft for all this time. It would be great if the pipe was the problem , but I suspect that the problem lies hidden elsewhere. Do you think draining down the system, as I described in post #9 would be worth a try?

The easy way to quote someone else's text, quicker than copy/paste - is to click the 'Quote' in the bottom RH corner of every post.

 

[BlueLoo]

The hose with the nrv hasn't been put in back to front has it?

 

[siliconeseal]

The easy way to quote someone else's text, quicker than copy/paste - is to click the 'Quote' in the bottom RH corner of every post.

Thats brilliant! Thank you Harry! How thoughtful of the forum Webmasters.

 

[siliconeseal]

The hose with the nrv hasn't been put in back to front has it?

Well if it had, then how did the setup work for the three years immediately following the installation of the EV?
I never realised how complex troubleshooting in plumbing was! Its like hunting submarines, or solving murder mysteries.
You have my respect gentlemen! I recently completed a Level 1 course in MIG welding. Lots of plumbing students were doing their courses at the same place (North West London College). as were budding Heating & Refrigeration engineers.

 

[BlueLoo]

Well if it had, then how did the setup work for the three years immediately following the installation of the EV?
I never realised how complex troubleshooting in plumbing was! Its like hunting submarines, or solving murder mysteries.
You have my respect gentlemen! I recently completed a Level 1 course in MIG welding. Lots of plumbing students were doing their courses at the same place (North West London College). as were budding Heating & Refrigeration engineers.

I will refer to the quote by Mr Sherlock Holmes.....

 

[polesapart]

1 Confirm that the directional arrow markings on the check valve (RHS silver valve) are towards the system.
You may need a mirror as your installer left the valve markings on the less visible side.

2 Unscrew the loop from that valve.

3 Confirm mains pressure through the loop by opening the left hand valve for a second or two.
Use a bucket or something to collect the jet of water you should get.

4 Anything visibly blocking the inlet of the check valve? Clean it off. Post photo if not sure.

5 If all the above checks out (mains pressure, no obvious gunk) your check valve is probably blocked internally.

Simplest would be to replace the whole filling loop, preferably one with two valves like
https://www.screwfix.com/p/r24-filling-loop/83905 or
https://www.toolstation.com/straight-braided-filling-loop-part-l/p83963
Obviously you will need to turn off the mains water and deprssurise/drain the heating system to do this.
Discard the nuts and olives supplied and fit directly onto existing.

6 You could of course replace the check valve only, but you'll struggle to buy one (flat face inlet x 15mm compression outlet) on its own.

 

[martygturner]

diaphragm gone on the expansion tank..

 

[polesapart]

diaphragm gone on the expansion tank..

wouldn't cause what the OP describes

 

[siliconeseal]

@polesapart, BlueLoo, Harry, Marty: Thank you Gentlemen!
Unfortunately other committments prevented me from tracing the source of the flexibe grey feed into the expansion tank. But many thanks PolesApart for your clearly explained & helpful post #37. I picked up the filling loop from Screwfix about 3 hours ago. I've ordered a bike pump with pressure gauge and Schrader valve coupler from Amazon, which is due for delivery tomorrow, for repressurising the air bladder of the expansion vessel, if this is required. I also ordered Jubilee clips from Toolstation to make my garden hose connection to the ground floor rad's escape valve watertight. This too is due in tomorrow.

Once all the bits'n'bobs are to hand, I will drain the system via the ground floor hall rad's escape valve, after bunging the two non-garage outlets in the loft water tank & shutting its ball valve, and opening the air-vents of the rads.

That done, I'll undo the compression nuts at either end of the flexible braided connector between the flexible grey feed to the EV and the EV itself, then remove this connector. I'll keep a tupperware container under the connector being loosened to catch any escaping water.

I'll then loosen the large diameter Jubilee clip holding up the EV, then rotate the EV to undo the water input feed at the top of the EV. My brother will be helping me out in the EV removal process. Once the EV is removed, I'll empty its water contents, and pressurise the air bladder to 1.5 bar with the bike pump.

Then back goes the EV into its Jubilee clip. Then the water inlet to the EV is screwed back on with some PTFE tape. The Jubilee clip is then tightened. Next, in goes the new loop connector from Screwfix, ensuring its in the right direction. As PolesApart recommends, I'll retain the olives from the previous loop connector, discard the olives from the new loop connector and tighten the compression fittings with some more PTFE tape (some on the threads of the connector males and some wrapped on the tube between the nut and the olive (to prevent weeping). ALL THIS ASSUMES THAT THE OLD OLIVES CAN SLIDE OFF their respective tubes, because if they are stuck in place then I will not be able to remove them in order to put in the compression nuts.

If the old olives are stuck in place and refuse to slide off even with WD40, then its Junior Hacksaw time, gingerly cutting into the olives without damaging the underlying tubing, ALWAYS A DELICATE OPERATION! Once the cut is deep enough, I'll use a flat screwdriver to wedge into the groove and twist to split the olive at that point. Please correct/advise me if I'm doing this wrong.

With the EV all connected up, it time to unbung the tank and fill up the system, see my post #9 for details of how I'll do this.

EDIT: I STRONGLY SUSPECT THAT THE EXISTING BRAIDED COUPLER IS THE FAULT. BECAUSE I ONCE TWISTED THE FLIMSY PLASTIC KNOBS ON THE VALVES THE WRONG WAY AND THE KNOBS SPLIT OPEN. I THEN HAD TO USE A PAIR OF GRIPS TO HOLD THE FLATS ON VALVE LUGS AND TWIST THE LUGS UNTIL THE FLATS WERE PARALLEL WITH THE BRAIDED LOOP. REALLY SHODDY CONSTRUCTION!

EDIT2 : THE PENNY DROPPED! I FINALLY UNDERSTOOD WHAT POLES WAS SAYING. IF I RETAINED THE OLD OLIVES AND THE OLD COMPRESSION NUTS THEN THERE WOULD BE NO NEED TO REMOVE THE OLD OLIVES AND I CAN PROCEED AS IF THE OLD OLIVES & NUTS ARE THOSE OF THE NEW COUPLING. OBVIOUSLY I WILL NEED TO APPLY THE PTFE TAPE AS I DESCRIBED EARLIER IN THIS POST.

 

[terryplumb]

You will need to shut off the mains cold water supply to the filling loop. It is not fed from the loft tank.

 

[siliconeseal]

You will need to shut off the mains cold water supply to the filling loop. It is not fed from the loft tank.

Thank you Terry, I know where it is in the pavement outside, the little white plastic wheel. But what I cannot remember is do you turn the wheel clockwise or anticlockwise to shut it?
EDIT: And once the mains is shut, open the cold water tap in the kitchen sink to drain out any remaining mains water BEFORE fiddling with the EV.

 

[terryplumb]

Most valves would be turned clockwise to close.
Don't you have an internal stopcock where mains cold water enters your property ?

 

[BlueLoo]

Most valves would be turned clockwise to close.
Don't you have an internal stopcock where mains cold water enters your property ?

Normally under the sink?

 

[BlueLoo]

To just slow things down a bit here...

The exercise is now to:
A) check that the cw feed is actually mains pressure and working?
B) check the nrv hosing and remove and replace?

You'll have to make sure the cw feed is exactly that. Else you'll **** water everywhere because you've turned off the wrong line.

Turning off the mains inlet (kitchen) should kill the flow if the above is correct.
The ****e, contract gate valves put in by plumbers are usually the cheapest on the shelf, so probably do not give 100% shut off.
To stop the pass through soaking you further, if your cw mains tap is indeed under the sink and feeding the kitchen directly (as it should) you might leave the kitchen cw tap ON whilst doing this work. You'll get a dribble, but better in the kitchen sink than on the airing cupboard floor.

Before you remove the hose, check, check and check again that the flow to it is off. If the hose remains stiff, it's likely still under pressure. I'd shut the valves on it and only undo it (at the EV end) once you've drained the ch system (I'll come back to this).

This way, you should be a dryish disconnect.

One disconnected, point the valve into a bucket and crack it open. It it dribbles, you may be on. If its under pressure, you've not turned off the water.
Assuming all is good, carefully disconnect the hoses and valves from the grey hose. Be gentle, put the open hose end in a bucket. Better still, use one of the valves in the new hose set to temporarily shut it off. You can never be sure....

Take the disconnected hose and fittings and go downstairs, make a cuppa and take a close look at it.
Is anything obviously wrong? Is it fitted the right way?
Does the valves and nrv operate properly? Do the lock when applying pressure in the back flow direction?

Why do this? You are looking to see the faults. Mich better to onow you've replaced a broken part rather than just guess. Oh, don't immediately throw it away. You may need it....

With the pressure released in the hw circuit, you can take the opportunity to do a full drain. If you do this, and, are quite happy to do it again, you can take the opportunity to drain the system completely, then chuck in a cleaner for a week or two and then drain it again. Either way, you need to redose with inhibitor on refill.

Take the opportunity with the system down to correct the bodge of the filling hose and EV support.
I'd secure the inlet hose locally to the ev tank and use a proper connector which can be shut off and removed between fillings.
Google it, you'll get the idea.

When reattaching the new hose, i wouldn't use anything in the compression joints. Very bad practice tbh. A clean joint should be enough. Reconnect carefully and dont under or overtight the fitting. Unless mangled by the dodgy ****er who put all this in, you should be ok . However, keep the spanners local incase you need to nip up further to stop any weeping.

Oh.
If you are able, get a number of an available local plumber before you start. You might find yourself in a rush to get one once you do.


You'll be fine though. Best of luck