Poor Gravity feed hot water pressure -possible improvements?

[jamin]

I have a vented hot water system from a cylinder in the cupboard heated by either the back boiler or immersion. It has 22mm pipe running round the maisonette.

2 years ago I fitted a new bathroom and ensured I fitted low pressure everything (shower head, shower pipe, taps, full bore isolating valves etc) and the pressure wasnt too bad given it only has about 1300mm height between the tank and the shower head. After the first year it started having the odd bad day when pressure at all taps was not that good. I checked the tank in the loft and it was full as expected. It seems to be doing it more often now, starts off good then after a while gets very poor but still this is not everyday.

A young plumber (I say young as he kept on referring to 'what he learnt at college') came round to work on the neighbours system and as we share the same loft space I mentioned the problem. He had a look and said there could be a partial blockage (the tank in the loft is clean however) but one thing he did say is the hot water supply pipe out of the top of the hot water cylinder turns immediatley at 90 degrees and runs over to the wall were it goes up in to the loft but the angle was actually slightly declined (ie 93 degrees) and should be slightly inclined. Could this cause an intermittent problem? I assumed it would be constant if it did. Would it be worth rectifying this as a first port of call? He mentioned it could create an airlock which would cause the poor pressure but wasnt sure if it could be intermittent

Also the hot water supply runs from the cylinder back up in to the loft only 500mm below the tank, over the front room, bathroom, toilet and down in to the kitchen where a spur supplies the kitchen taps (15mm) and continues at 22mm to the bath (with another 15mm spur to the bathroom sink). I could quite easily run a 22mm feed to the bath above the skirting in the front room and shorten the run by at least 3/4 to the bath. Would that offer a noticeable improvement as the length is considerably reduced?

Could the system be partially blocked? If so, how would I purge the system to clear it ?

Sorry for the long winded post and I hope someone can help, I wanted to explain the situation as clearly as I could but not bore someone to death with my ramblings! Any advice will be greatly received.

 

[dcawkwell]

A moving blockage. Perhaps limescale at the bottom of the hot tank.

 

[onecog]

Do you have a washing machine with H & C valves ?
Fix one hose across both wm valves and open them both.This will get rid of any air or crap in the pipework.

 

[maltaron]

I cannot explain the intermittent problem but have yo got flexible connections to your hot taps? Allthough 22mm nominal these tend to be fairly small bore.

 

[tincup]

Hi

I would check the neck of the tank and pipework off of it for limescale.

HTH

 

[jamin]

Thanks for all your suggestions.

What should I try first?!!!

If I was to attach the washing machine hot supply to the cold surely I would need to drain the system otherwise were would all the crap go? Therefore, would I need to open the drain at the bottom of the cylinder and drain the entire system (first blocking off the storage tank outlet). Leaving the drain open, turn on the cold washing machine feed to back flush the system?? Would that be right?

Do I risk irreversible damage removing all fitting to it to see inside the cylinder and see if there is a blockage?

The hot pipework to the bath has no flexi pipes as I hard mounted 22mm pipe to the bath taps (although the sinks are both flexi)

Thanks for the pointers, does anyone know if the 90 degree statement the plumper made is true?

Thanks once again, could someone say what they would do first as I have too many options

BTW the shower this morning was excellent, so good I spent a extra few mins in it!

 

[onecog]

If you use the WM hose and open the hot bath tap you will soon find out if you have a problem in that pipe run.With no hot taps open all of the water will go up the vent into c/f tank and out the overflow.You could run a hose pipe into the loft.push it down the c/f pipe a few feet,open the bath tap and get someone to turn the hose on.If your problem is limescale or whatever then you might need to remove the cylinder and take a look.It is difficult for someone to give advice without seeing the set up.
You might need a plumber.