No hot water - inlet pipe cold

[Robert Wooler]

I have an issue with getting hot water which has only just happened.

I have a gravity fed system for heating/hot water which has been working fine for some time (oftern water seeming a little hot)

My hot water is not getting heated any more, so i checked the pump and that seems as though its fine, even unscrewed the brass screw to release any air. The next in line is the three-way valve for heating and hot water (delivering to cylinder), the pipe was hotter on the heating and only milder on the hot water, so i set the three way valve to MAN, i now have the same heat on the pipe at both ends A and B, the hot water pipe goes upwards across and downwards its at this bend the pipe is cool, and from this point into the cylinder it is cold.

Also to add, my pump gets very hot

The output from the cylinder back to the boiler is cold

Any ideas?

Rob

 

[Hugh Jaleak]

Firstly, need to ask what make/model of valve have you got? Then, if you set the system to HW only, what happens? Initial thoughts are either faulty valve or a blockage on the cylinder coil/pipework, but really need to know if valve is operating correctly first.

 

[Robert Wooler]

Cheers for reply

There is no brand on the motorised valve, I have it in manual mode now

The B pipe going to cyclinder is getting hot but goes cold before it reaches the cylinder, it goes cold just before an elbow joint before going down into the bottom side of cylinder.

I’m pretty sure there is a blockage but don’t know how to a) verify it is a blockage and b) how to remove it

I can feel the area that goes from hot to cold on a selection of piping, before the bend it’s hot and after the bend it’s cold

Even when valve was in normal mode and water only the radiators would still get hot

Rob

 

[Hugh Jaleak]

Got called out to look at a job, which ironically seems to be a blockage! Try the magnet test first, that is run a magnet along the pipework to/from the cylinder coil. Copper/brass is Non Ferrous, so a magnet wont attract, but any blockage will cause the magnet to be attracted to the crud inside the pipe.

If it is blocked, the only solution I'm afraid is to remove and replace the affected section.

 

[Robert Wooler]

Hi there, thankyou for getting back to me, i had tried a magnet along the pipe which had no effect, ive tried tapping/knocking pipes too, i am beginning to think along the lines for air trapped now, as not far from where it goes cool, is an automatic air vent, which has some gunge around it, which i don't think it should there, im hoping to replace it in the morning, as the part is relatively cheap and would eliminate that as a cause.

I have been getting some noises which ive not really thought could be an issue, and that is when the boiler fires up for my heating and water i get a slurge noise whilst all the water seems to be dropping into the boiler, its like a big wooosh and then what sounds like a flood of water entering the boiler, but just lately, its been like, disrupted flood noise, sort of like wooshing, and then trickling noises and then back to wooshing as the boiler/heating fills up and the water gets circulating.

Rob

 

[terryplumb]

Sounds like a lot of trapped air . Have you tried to bleed the coil using the vent you mentioned ?
Have you ran the magnet along the feed from the F&E tank to see if it is blocked ? There may not be enough water in the system.

 

[Robert Wooler]

I have had air stuck in the system before when i had a new pump fitted, this was quite some time ago, i was told there was air in the system because of some cap that had been tightened too much, not sure what he was on about back then, its a £4-5 part and can be swapped easily so that will rule one thing out, sadly i'm no plumbing engineer so wouldn't know how to bleed the coil, it it means removing nuts and potential flooding then they will be my last resorts, im just a mere graphic designer and am relying on the kindness of others like you to point me in the right direction.

I never thought of checking the tanks up there to see if anything is in them and that they are functioning ok, they will be heavily sludgy by now i guess, this seems coincidental with all the bad weather we have been having. I will check them in the morning, and yes i will run the magnet across them. Fingers crossed

Rob

 

[Harry Bloomfield]

I will check them in the morning, and yes i will run the magnet across them. Fingers crossed

Just to be clear, you should be using the magnet to check if it is attracted to any of the pipe. If a pipe becomes obstructed, it will be obstructed with iron oxide from your radiators rusting internally - therefore you will feel a slight pull on the magnet, where the obstruction is located inside the pipe.

 

[Robert Wooler]

ok, ive ran a magnet across the pipes after the valve to the cyclinder and no pull the magnet, or at least i can feel, it is tight in there, and some of the lagging is hard to remove. Ive also checked the expansion tank in loft, this has some water in it, not a lot, it looks a murky brown, but that could be my lighting, the ballcock works if i push it down a little, more water flows in. I do have one question, whilst i see fe tanks with ballcocks on youtube, they have the arm straight as in up and down action, who ever has installed mine, its slightly angled, what i mean is the hinge part is on a slight angle so the ball arm and ball go up and down with a slight forward and backwards effect, is this normal to install this way? have they done it this way to alter when the water is triggered?
Rob

 

[terryplumb]

Some float arms are straight with the ball on the end ,some have the float arm bent at a right angle ,if that's what you are describing . As long as it allows water into the tank ( and the water level only needs to be 3/ 4 inches deep) I wouldn't worry too much. But the pipe that runs from the bottom of the tank feeds the system and it is that pipe that can block , so run the magnet down that pipe ,particularly from the ceiling down to where the first joint is ( usually a Tee),to check it's not blocked.
Can you show us pics of the Pipework in and around hot water cylinder ,and specifically those going to its coil.

 

[Harry Bloomfield]

That is fine then. The arm shouldn't be moving at an angle, but so long as it is working to keep the F&E tank topped up, it's OK.

 

[Robert Wooler]

Hi, ive took apart and cleaned the automatic air lock (Honeywell model where you can turn it off and unscrew the top)

Ive re-done the magnet test, and im getting a pull along on one parts of pipe

I will attach pics of my system and label for reference

Rob

 

[Robert Wooler]

update, i did the magnet test again, and at the part of the pipe i've indicated in poss-block.jpg image, the magnet pulls, infact the magnet holds there, this is before it reaches the bend to come back down and into the cylinder, at entrance into cylinder it feels cold, also the out from the cylinder feels cold and gets warmer the as it disapears under the floor of the cupbload (pic above with red valve), i have the pump on 3 for a bit, in the hope extra flow might move any debris, but i think im screwed.

I saw a pic of someones pipe that showed how narrowed it had gone for them, can any cleaner added to the system help break this up?

Up in the loft ive just found an empty sentinal x100 inhibitor, god know when that was lasted added

Rob

 

[HERTS P&D]

Is there a bleed valve on the pipe work going into the top of the coil on the side of the cylinder?

Post some pictures.

Andy

 

[Robert Wooler]

Is there a bleed valve on the pipe work going into the top of the coil on the side of the cylinder?

Post some pictures.

Andy

do you mean the air vent? this is at the highest part of the pipework towards to cyclinder, thumnail attached, if so, ive had this stripped down and cleaned, when i opened the vale again, i had a rush of air, and tiny trickle of water

Rob