Hot Water - Reduced Flow

[BarryFig]

Hi All,

Following installation of a new hot water cylinder located on the first floor of my house (indirect system) I noticed a drop in hot water pressure. The installers couldn't find any fault but hinted at a possible partial blockage in the pipework predating their work! This situation has continued now for some months and I haven't been able to find a plumber interested in solving my problem (guess there's other more lucrative jobs to do).

As a reasonably skilled DIYer I thought the best way was to use the old washing machine trick and hook up the mains and hot supply (normally feeding the washing machine) and flush the cr*p out.

The risk is that I might blow the cylinder but if the cold feed to the cylinder is in the closed position, I reasoned that the water (now under mains pressure) will exit via the expansion pipe in the loft along with the offending cra*p!

It's not an airlock incidentally (sometimes you can hear a noise downstairs when the hot tap in the kitchen is turn on) sort of humming ossolating sound which will stop if you turn the tap off, then on again.

What do you think guys?

regards

Barry

 

[Softus]

How much pipework did they keep, and how much did they replace?

Is there a Surrey or Warix flange that they reused?

 

[JPC]

i went to a job on friday.

after running the hot tap for about 30 seconds it runs slow and then nothing.

Gate valve feeding cylinder ok

Kitchen mixer tap trick...no air locks

I then asked the customer to do the kitchen mixer business (your doing it via the washing machine..same idea/thing)...i went upstairs to the loft...all the water was coming out of the vent...so placed hand over it....with in 15 seconds a "plug" of insulation shot out of the feed pipe and back into the CWST...
i half suspected that as there was floating insulation in the cwst when i first looked in

 

[twgas]

is the problem at all the hot taps

 

[BarryFig]

Thanks guys, really appreciate this. In answer to (hopefully) all points raised:

I suspect some form of foreign body has entered the pipe work and insulation debris sounds exactly right because the problem has 'moved' over time indicating to me that the body is floating in the pipe and not lime scale, for example, which should come to rest at the lowest point in the system and stay there (logically).

Most (if not all) of the pipework was retained as the cylinders were the same size. Only an elbow joint connector looked (at the time) new.

As regards 'Surrey or Warix flange' I am no plumber but can tell you that the hot supply leaves the tank via a 90 degree elbow. A short length of pipe then connects to a tee down to supply the taps and up to vent to the CWT. Does that cover your question?

My water runs slow, full stop. I estimate it to be about 15 to 20% of the flow rate I would normally get.

Three plumbers have said it's not an air lock (but won't take on the job because they had better things to do, I guess, which is fair enough).

All hot water supply is now affected save for a power shower that takes its supply from a tee situated only 50cms from the top of the cylinder.

So a mains flush with the water being forced back up the pipes to discharge in the loft shouldn't result in a blown cylinder, right?

Any other ideas would be very grateful to hear about as I have a house of 5 and we cant all use the shower!

Many thanks

BF

 

[Mcfly1]

I've used a plunger on the outlet out of the header tank before- haha

worked for me!

 

[BarryFig]

Hi Guys,

I used the mains to flush the partial blockage of my hot water supply.

Although nothing was ejected from the overflow pipe in the CWT in the loft, hot water was restored icon_biggrin.gif Now its reduced again icon_sad.gif

The pressure of the mains was not sufficient to blow the cause of the blockage out of the overflow (it only move it back up the pipe).

Would a plumber have any flushing kit (that would increase the water pressure, so its greater than mains pressure) which could be hooked up to push out the cr*p in the pipe? I know they power flush central heating but that's specialist kit for that job rather than flushing supply pipes.

Any ideas?

cheers,

Barry

 

[Softus]

I used the mains to flush the partial blockage of my hot water supply.

Although nothing was ejected from the overflow pipe in the CWT in the loft, hot water was restored icon_biggrin.gif Now its reduced again

That isn't conclusive. One possible cause is a fragment of foam insulation inside the cylinder.

Would a plumber have any flushing kit (that would increase the water pressure, so its greater than mains pressure) which could be hooked up to push out the cr*p in the pipe?

No. The first step is to cut into the pipework to home in on where the obstruction is.

 

[BarryFig]

Thanks Softus. I think dense foam is a high possibility (the sort you get as insulation around HW cylinders).

I am fairly sure that the blockage is not in the cylinder since a power shower (without power on, so it's gravity fed) evidences the same pressure if switched between hot or cold. The power shower is the first branch off the hot supply.

I think the problem is somewhere later in the run, after the 28mm pipe reduces down to 22mm. Problem is the pipe is under the first floor then it bends up behind the soil stack, so it's not possible to do as you suggest, without major damage to the flooring and titling.

If you had enough power, I think a flush would work but if there is no such piece of kit (to increase the flow but through the system to flush out the obstruction) then I and royally scr*wed as far as that cunning plan is concerned.

Perhaps I need to find a way to chop out that pipe and run another supply from HWT, unless somebody else has a better idea?

cheers either way for the contributions,

Barry

 

[TicklyT]

....Would a plumber have any flushing kit (that would increase the water pressure, so its greater than mains pressure) which could be hooked up to push out the cr*p in the pipe?....

There's a pretty good chance of splitting the hot water cylinder if you increase the pressure in a vented system.

 

[twgas]

try cutting pipe after shower tee, rig up a hose from it to outside, cap vent pipe, then try your wm trick and hope it blows your blockage out, may need a few old towels just in case

 

[BarryFig]

Once again, many thanks.

If the cold supply to the HWT is closed off, I thought that logically it cannot split/blow. Thinking again, like a steam engine with too much steam there might be the flaw in my logic..................

Cutting the pipe as suggested might work as the distance between the site of the blockage (my guess) and the (proposed site of the) cut pipe is 3 metres max. As all my kit assumes 22mm max. pipe, I don't have the pipe cutter etc. to do the work or a pipe large enough to take to waste water away. Guess I need to get myself off to Screwfix ......

many thanks,

Barry