Low hot water pressure/throughput

[Reg.T]

My ex (and children) live in a house with a hot water cylinder and boiler on the ground floor and a header tank for the HW system in the roofspace (eff. 2 floors above). There is a bedroom/bathroom/shower also on the 2nd floor, and the sink would sometimes stop delivering HW when the header was drained. Shower is pumped and uses hot & cold (pump is on 1st floor).

Last year a new boiler was fitted, and since then she reports a much worse delivery of HW, such that running a bath (on 1st floor) requires planning, 2nd floor sink HW virtually non-existent, and the shower has to be used in bursts as it seems to get starved of HW when running. My assumption is that some scale may have been disturbed in the HW cylinder during boiler changeover, and is now partially blocking the pipes.

Any thoughts on cause and solution welcome.

[jsabine]

It's not something as obvious as a valve or stopcock not having been fully reopened at the end of the works, I take it?

[Canardly]

As above, is or are the three way valve(s) operating properly?

[Reg.T]

To clarify - it is not a combi-boiler system. HW system is effectively independent of the CW (ignoring the refill rate of the header tank).

It's not something as obvious as a valve or stopcock not having been fully reopened at the end of the works, I take it?

No, I think the CW pressure is OK (now that an issue with the main supply pipe has been fixed ), and the HW header tank does sound like it fills (and stops) as expected.

As above, is or are the three way valve(s) operating properly?

Do you mean the valve that directs heated water to CH system or HW tank (to heat the HW)? I think that is OK - the HW is hot, there just isn't much of it.

[Canardly]

As you suggest could be crap in the primary system. Was the system purged/flushed when boiler was replaced?

[rafletcher]

The boiler operates on the primary loop, inside the hw cylinder. Changing the boiler will have zero affect on the secondary loop - which delivers the hot water from the cylinder to the taps. How big is the header? Should be maybe double the size of the cylinder. If she's getting water starvation then it'll be due to flow restrictions either from the header to the cylinder or from cylinder to point of use or lack of head in the header - not refilling fast enough. Pumped showers can empty headers double quick, leaving zero head for anything else. Is the cw delivery ok - this will be direct from header to bath / basin taps (except kitchen which should be mains fed).

[Reg.T]

I don't think the problem is in the primary loop, as the HW does get heated. The problem is HW flow. My impression has always been that all CW  (and header tank) are mains-fed. The shower used to empty the header, but not since the new boiler installed. I realise that they probably didn't need to drain the HW tank during the boiler swap, but the boiler is directly beneath/behind the tank and the problem stems from the time of the replacement. I assume it is related as nothing else in the HW delivery system has changed. The HW tank is 15-20 years old I think.

Flow is poor even when header full, so I infer that there is a flow restriction, but could be anywhere between header and taps. What options do we have to try to trace or remedy?

[Tim Hall]

An airlock in the cold feed to the HW cylinder can have the symptoms you describe. I had similar on a shower mixer (but on the cold side) and fixed it by conecting a hose to the shower mixer and blasting it with mains pressure back to the cold tank.

[rafletcher]

An airlock in the cold feed to the HW cylinder can have the symptoms you describe. I had similar on a shower mixer (but on the cold side) and fixed it by conecting a hose to the shower mixer and blasting it with mains pressure back to the cold tank.

A distinct possibility. I used to have an airlock problem, and used to cross connect the cw mains incomer in the kitchen to the hw tap feed to back-pressurise it

[aidan.f]

Had to use that trick once to remove remains of dead bats from header pipe that were restricting flow. iirc used a wet n dry cleaner to empty the tank, ucky job.

[Reg.T]

Thanks for the responses, all.

I'm doubtful that it is an airlock because it never occurred before the boiler change, when the shower would drain the header tank on occasion and give every chance for an airlock to form.

So, check the header tank lid is in place and that tank outlet looks clear inside?
Use garden hose onto HW system drain point to force water back up into the header?

[aeolus]

We had a very similar problem, tried the reverse flush cold/hot etc.

In the end we took out the hot water cylinder and found it had a huge amount of a calcium deposit floating around in suspension without actually totally blocking the outlet - just reducing the flow.

I cut it open and was amazed at the quantity of white material - many inches in the bottom - it is now in Bath College as an exhibit for plumbing students !

Not sure if your problem is in such a hard water area as Clevedon.

Oh off subject hows the Strada fixed bike going ?

R.

[Reg.T]

Any idea how old your cylinder was? (I do appreciate that age is only indicative at best). I'm between Bristol & Bath, so yes we have hard water too.

OT: yes, it's all good thanks. Have been riding it for a year now, and reckon it's carried me on 2/3 of my >14K Km this year, (including 26 AUK points & 6.25 AAA on fixed). Had a bit of trouble getting the right brakes (basically cos Wiggle said the ones I'd bought were 57mm not 49mm), but that's sorted now, and I've recently swapped from 90mm to 80mm stem which seems better for me. I'm currently aiming to complete both of the AUK Fixed awards and PBP on it in 2015. Your SS still going well?
/OT

[aeolus]

The cylinder would have been about 15 years old (copper) as I installed it when we first moved here replacing an old galv one.
The calcium stuff was strange - some was hard and some more soft putty like when drained down - when water was added it was very cloudy in suspension - my plumber had not seen anything like it to the extent we had. A mate (another plumber) who was lecturing at Bath College thought it rather unusual and took it to the College !.

'Off subject', my Strada is going well (3 speed fix - age !) - I had to increase the drop on the rear brakes to accommodate the wheel going backwards in the track ends.
I've also ordered a Croix de Fer 30 (gears bike with good clearances)  as I'm stuggling with the hills around here for longer distances !

Best of luck with both the hot water and the PBP !

[rogerzilla]

Assuming a normal vented cylinder, backflush the affected taps from a mains pressure tap.  I had to do this frequently as the aerators on my bath taps are very fine and tend to accumulate bits of scale (I've since drained, dried and actually vacuumed out the cold cistern in the loft, which has solved the problem for a few years, hopefully).  Also, on completely draining the system, it often needs a backflush to clear airlocks and fix slow-running taps.  My last two houses have been like this.

Buy one of the Hozelock universal tap adaptors (about £10) for the bath tap and connect the other end of a hose to your outside tap or any other mains pressure tap.  However, if you use an inside tap you'll probably need another one of said adaptors.  100psi of mains pressure will shift anything back up the pipe to the bottom of the cylinder (or the cold water cistern) where it can sink harmlessly to the bottom.