Low hot water pressure from combi boiler - advice please

[richardygrub]

Can anyone offer me some advice....

Two weeks ago the hot water flow rate (at all taps) from my combi boiler (Worcester Bosch 24Cdi) dropped from it's usual 9L/min to less than 4L/min.

Suspecting the boiler I called Worcester Bosch for one of their fixed price call outs. The enigineer came and replaced the water-water heat exchanger, diverter valve, and pressure relief valve. He left saying that although he has replaced the parts, it hasn't fixed the problem and that he suspects a problem with the pipes and that I'll have to get a plumber to sort it out. To be honest his competence didn't fill me with confidence.

Strangely, after he left I checked the hot water the the flow rate was back to the normal 9L/min. However the following day it had dropped back to <4L/min. The only thing that happened in between was running the dishwasher.

Also, now when the hot water is running knocking noises can be heard in the system.

So now I am £245 poorer thanks to Worcester Bosch and still have the problem.

Any advice greatfully received.

Richard.

 

[gas4you]

Could be you have a partially blocked inlet filter on the cold water inlet on the boiler.

Could be a problem external to your boiler.

Have your cold taps been affected?

 

[richardygrub]

Thanks for the reply Dave.

All cold taps are fine with good pressure. All are fed directly from mains supply.

If it is a partially blocked inlet filter, is this something the Worcester Bosch should have diagnosed, or is it considered external to the boiler?

There is a Liff Limefighter on the cold feed to the boiler. Is there anything on these (such as a filter) that could restrict the flow?

If it is a problem external to the boiler on the hot water side is going to be in a very short length of pipe because it tee's off to supply upstairs bathroom and downstairs kitchen 1.5 meters after leaving boiler, and there is poor hot water pressure everywhere.

Unfortunately though the Tee is under floorboards as the boiler is in an upstair cupboard.

The engineer suggested connecting mains pressure cold water to the hot water pipes to blow potential blockages out. Could this damage the boiler?

Cheers again.

Richard.

 

[gas4you]

I feel the problem will be before the boiler, not after.

You could try removing the Liff and checking it, but I don't think that will be a problem.

Still would look for and check the water inet filter on the boiler.

Cold mains pressure won't hurt the boiler. That is what it should be getting anyway to work.

 

[richardygrub]

Cheers dave, Il'll check these things out tonight.

The engineer said that he suspected something on the hot water side based on how fast the system re-fill after he drained it. Although he couldn't prove it he thought there was ample pressure to the boiler.

 

[richardygrub]

Just had a look at the installation and servicing instructions. It appears the inlet filter is a U shaped device that sits inside the cold water in connection on the diverter valve. I cannot (well hope not) believe it was not checked or replaced with the diverter valve.

I don't feel confident enough to check myself as it requires the removal of the filling loop, head exchanger, and diverter valve. Can't risk breaking it completely!!

About to try connectiing mains pressure cold to hot water side using washing machine connectors. This will at least rule out the hot water side if it doesn't fix the problem.

After that was thought I might remove the Limefighter and connect soeme flexible hose and a tap where the water would have flowed into the limefighter. This should enable me to test the mains pressure just before it enters the boiler.

If anyone has any better ideas I would love to hear them because them time is approaching fast where I any going to have to shell out more cash to get someone (who will take pipework into consideration) to take a look.

Thanks again.

Richard.

 

[nickso]

After that was thought I might remove the Limefighter and connect soeme flexible hose and a tap where the water would have flowed into the limefighter. This should enable me to test the mains pressure just before it enters the boiler.

that should prove the pipework. if he changed the entire diverter then he has also changed the filter.

 

[baxpoti]

If the engineer diagnosed the problem incorrectly and changed parts unnecessarily this is of no significance.
Worcester took your money to fix a problem, and they obviously haven't, then they have not fulfilled their contract.

Demand a refund or get them back to sort it out.

 

[JPC]

i have to agree with baxpoti, once you have proved water supply to boiler, as you desc, then go back to them and have words

 

[richardygrub]

I will be doing exactly that. Obviously need to rule out the pipework before giving tham a hard time.

 

[richardygrub]

As stated in previous posts I'm not an expert in the working of a combi boiler.

I was going to use the trick of connecting main pressure cold water to the hot supply to clear any airlocks or blockages.

However, I have seen a number of posts (including on this site) that state this cnnot be done with a combi.

Can anyone confirm whether this is something I should (or not) be doing.

Thanks again.

Richard.

 

[richardygrub]

I thought I would post a closing reply because as of about an hour ago the problem is finally fixed.

After spending a fair bit of time any money ruling out the pipework external to the boiler I called Worcester Bosch again.

The engineer had the it fixed within 15 minutes of his arrival. It was the flow regulator. He showed me the old one and it was visibly knackered. The ruber washer on which it is seated had broken up and was blocking the regulator.

The orginal engineer must have taken the knackered regulator out of the old HE (which didn't need to be replaced) and put it back in the new one.

Se in the end it was a £1.94 piece of plastic which has now cost me over £400.

I feel a complaint to Worcester Bosch coming!!

Thanks to everyone that offered advice.