assistancee required please guys

[iguanamark]

Afternoon guys,

have an issue at the present, wondering if you can give me some advice to see which way to proceed.

My father-in-law got me a boiler change (BBU-Combi) in Surrey, and I live in Devon. When I got to the job, I opened up the mains cold water & felt there was enough pressure (no pressure gauge used). I changed the boiler & after the job I got a call from the customer saying the COLD water dropped in pressure when 2 taps were open. I asked my FIL to go back & check it out. He mentioned to the customer that the lead incoming pipe may be furred up, therefore, get a new 25mm alkathyene pipe installed & maybe get the water board to check the pressure. They got the new 25mm pipe in, however, pressure still drops dramatically when 2x cold taps open. The water board were supposed to come in last Wednesday just gone, however, customer has not been back to me whether they have been or not.

Customer threatening to take me to the small claims court, because she says she has been given an inadequate & ineffective boiler (Vaillant Ecotect Plus 831), for which I have explained that is not the case. She had a gravity-fed system before hand, which never had an issue with lack of pressure, to which I explained the differences in systems.

As it stands at the minute, the 25mm comes into the house, about 10inches, before dropping down to 15mm, before going about 2mtrs to boiler & another 3mtrs to bath & basin.

I can't see that there's anything obviously wrong, so just wondered if anyone has had anything like this before, whether it be dealing with customer like this, or an issue on incoming pressures.

Thanks in advance,
Mark

 

[ecowarm]

You really need to check flow and pressure before installing a combi or an unvented cylinder IMHO

 

[bspareltd]

this is common on combis ,for hot water but it should not affect cold water!

 

[TBServices]

Unfortunately pal, you didn't do the checks so its on your head really, some places just have bad mains. There's streets round here where everyone has gravity systems cos of the poor mains pressure/flow.

Maybe a small booster such as the salamander would do the trick.

 

[nickelarsed]

how can a combi cause the cold taps to lose pressure or flow? Sounds like it's a mains issue and she needs on eof these:

Salamander Home Boost mains pressure booster pump

but I don't see how a combi can be responsible?

 

[Howsie]

Take 22 to boiler and then split to basin etc after. May help a little but as others have said...

 

[kozak1968]

Basic check would be at the cold sink tap, did you open the tap fully. did you check the stopcock in the street and house is fully open? After that put a guage on the main to check the pressure. Do any of the neighbours have combis?

 

[REDSAW]

you been twice and not checked the flow rate?

looks like you will have to install a 200 gal cold feed tank then to feed the cold taps to the bathroom keeping the kitchen tap on mains!!.
then again whats the hot flow like??????????????

 

[iguanamark]

i actually installed a combi for customers dad, directly opposite. Same road, no issues

 

[iguanamark]

thanks everyone for your replies.
It's definitely not affecting the hot water only, mainly the cold water!! Although I have a pressure gauge, I only use it when I think there's a possible issue once tap/s opened.

 

[mutley racers]

what has happened here is the normal situation when you change a gravity system to a combi. When 2 cold taps are used the pressure is redced dramatically. Like opening a tap in the kitchen with a shower. Unless you have over 18litres a minute or what not. it must just have been what she was expecting. Is the pressure ok with one tap open? It sounds like it is from your post

 

[iguanamark]

what has happened here is the normal situation when you change a gravity system to a combi. When 2 cold taps are used the pressure is redced dramatically. Like opening a tap in the kitchen with a shower. Unless you have over 18litres a minute or what not. it must just have been what she was expecting. Is the pressure ok with one tap open? It sounds like it is from your post

pressure ok with one tap open ...... just when you open a second one. I've never had a issue with the cold mains being reduced this much ...... that'll teaech me lol

 

[GasmanxxxR1]

combi is one tap operation, get her dad to explain it to her

 

[AWheating]

the hot and cold water are the same pipe/supply, so of course the hot can effect the cold . what you have is a poor flow rate. the water board will only garantee about 9 litres per min from memory. So when you turn the hot tap on the cold will have to share this 9 litres per min with the hot. if the hot tap has less restriction than the cold then it will get more flow or vise versa.

pressure and flow are two completely different things. You need to measure the dynamic pressure and flow rates of the cold main and if unsuitable for a combi boiler then fit an alternative system.

 

[jackyp1234]

did you fully open the stop tap up after fitting the combi, silly but you never know...

 

[iguanamark]

yeah, did a double check afterwards 🙂

 

[Whyme]

if you fit a combi or not that will never effect the flow on just the cold taps only if the hots run at the same time. regardless of mains changes is the stop tap in the house the one you turned off when fitting the boiler, have you checked the washer hasnt dropped or changed it ? its a cold mains problem if it happens when 2 cold taps are run not hot..it may well have been a problem anyway without you checking who knows. whats probablely happend is the've gone from tank fed bathroom cold now to mains and the problem wasnt evident before..

 

[mutley racers]

Oh sorry, I just read the post again. 2 cold taps. I was on about a hot and a cold. Forget what o said!!!

 

[Bronze_tap]

So you've got a few options:
1. Fix the root cause:
a. Check that ALL lead had been removed, maybe there is a bit still left somewhere upstream. (Like they replaced only a section of the lead with plastics initially, and now theu just went up to that plastic section, leaving the lead still upstream the middle plastic section.
b. Check all connectors/stoptaps for obstructions/blockages.
2. Mitigate the problem - get either:
a. 50 - 100 L expansion vessel, and fit it to the cold feed, with no-return valve to the outside+ kitchen cold.
b. 200L Water tank in the loft + pressure booster (pump with vessel)
c. Dial the hot water temp down to 40 - 42 degrees C on shower flow rate, so no need to open the cold tap. For dish washing let the owners up the temp by opening the hot tap partially, increasing the temp to 50 or so degrees.

 

[Mike Jackson]

So you've got a few options:

c. Dial the hot water temp down to 40 - 42 degrees C on shower flow rate, so no need to open the cold tap. For dish washing let the owners up the temp by opening the hot tap partially, increasing the temp to 50 or so degrees.

And the problem will go away because the customer will contact legionnaires disease and die. Okay perhaps a bit melodramatic but hot water should be supplied at 50 degrees or more to prevent bacterial contamination, particularly at showers etc. where droplet inhalation is most likely.

This post should be a lesson to everyone, check pressure and flow of the cold main before fitting a combi and explain to the customers the drawbacks as well as the advantages. I always look for twice the flow rate required by the combi as a minimum to give a decent performance.